While Sikhs believe that Sikhi/Sikhism has borrowed nothing from Hinduism, here are some counter facts.
There is a new breed of Sikh scholars who bend backward to prove Sikhism has taken little or nothing from Hinduism. All they need to be told is that of the 15,028 names of God that appear in the Adi Granth, Hari occurs over 8,000 times, Ram 2,533 times, followed by Prabhu, Gopal Govind, Parbrahm, and other Hindu nomenclature for the Divine. The purely Sikh coinage ‘Wahe Guru’ appears only sixteen times. Source
Similarly, there are claims that Sikhs don't celebrate Diwali but Bandi Chor Diwas, even though, Guru Amar Das still called it Diwali . While other Sikh festivals like Hola Mohalla coincides with Holi. And Baisakhi predates Sikhi. Even the tradition of langar even though the similar concept of public feasting predates Sikhi. No Sikh festivals coincide with Muslim festivals, the other dominant religion of India in the 15th century.
Then there are claims that Guru Nanak didn't wear Janeu, even though he questioned the hypocrisy of wearing one without good actions. In fact, as per the earlier authentic sources, he did wear Janeu and ordained Tilak.
Here is an old Sikh painting of Guru Nanak (seated in the middle) along with Bhai Bala and Bhai Mardana. His Tilak on the forehead can clearly be seen. There is a Rudraksha Mala in his hand. Notice his ears are also pierced. A Sikh scholar has also posted in detail that ear piercing was the norm among the gurus.
Illustration from Janamsakhi. Sikh painting (c. 1800)
Guru Nanak meeting Sheikh Sharf. Illustration from Janamsakhi. Early Sikh painting (c.1700). Guru Nanak (centre) is clearly shown with a Tilak and Seli Topi.
Another depiction of Guru Nanak (second from left) from the 300-year-old Baba Ram Rai Darbar. Again, his Tilak is very noticeable.
Painting of Guru Nanak, seated in the middle, with Bhai Bala and Bhai Mardana. His Tilak and Vaishnav Seli Topi can clearly be seen.
Another painting of Guru Nanak with his son Sri Chand. This painting is from Dera Baba Nanak Gurudwara which was set up by the descendants of the Guru.
Here is a personal collection of Guru Nanak's Seli Topi, Rudraksha, Shaligram, and his handwritten copy(pothi) preserved by descendants of Guru Amar Das who had set up their headquarters in Guru Har Sahai (Punjab).
Even the Sikh khanda symbol has been seen in similar forms been associated with Shiva.
Similarly, in the (prachin) Panth Prakash (page 850) , it is mentioned that at the time of his wedding, Guru Govind Singh wore Janeu.
In fact, the gurus read and praised about Vedas. Guru Nanak Dev wrote, “What can the Riches of Vedas do for a person who does not possess intellect”.
The original Guru Granth Sahib had depicted the 10 gurus around Maa Durga on its cover.
The oldest known copy of Dasam Granth whose authorship is attributed to Guru Gobind Singh. The date on the manuscript is 1698. The cover shows Guru Gobind Singh praying reverently to a Goddess who mounts on a lion.
Almost 50% (16/36) of authors of Guru Granth Sahib were Brahmins. This includes the 11 Bhatts and 5 Bhagats (Beni, Jayadeva, Surdas, Ramanand, Parmanand). The Bhagats lived before the advent of Sikhi. The descendants of the families of Bhatts have not accepted Amrit and initiated into Khalsa order.
An illustration of Baba Budha anointing Guru Arjan Dev with Tilak. Frequently depicted in historic Gurudwaras. Guru Ramdas tilak anointment is mentioned even in Guru Granth Sahib.
ਰਾਮਦਾਸ ਸੋਢੀ ਤਿਲਕੁ ਦੀਆ ਗੁਰ ਸਬਦੁ ਸਚੁ ਨੀਸਾਣੁ ਜੀ
The Guru then blessed Sodhi Ram Das with Tilak
“Sikhs are still to a certain extent Hindoos. They worship the same deities as the Hindoos, and celebrate all their festivals; they derive their legends and literature from the same sources and pay great veneration to Brahmins.” - Observation by Wilson quoted in EIC gazetteer, 1858
Sikh army battle flag featuring Durga on the military banner
Maharaja Ranjit Singh worshipping Durga
Frescoes of Durga in Sikh Gurudwara at Nurungabad c.1720 AD
In Gurugranth Sahib, Gurunanak calls his god by the name of Hari and says that their god is chaturbhuj (four-armed), Shyam Sundar(blue-skinned), and jadim rai(kings of Yadavas).
Maalee Gauraa, The Word Of Devotee Naam Dayv Jee: One Universal Creator God. By The Grace Of The True Guru: Blessed, blessed is that flute which the Lord plays. The sweet, sweet unstruck sound current sings forth. Blessed, blessed is the wool of the sheep; blessed, blessed is the blanket worn by Krishna. Blessed, blessed are you, O mother Dayvakee; into your home, the Lord was born. Blessed, blessed are the forests of Brindaaban; the Supreme Lord plays there. He plays the flute, and herds the cows; Naam Dayv's Lord and Master plays happily.
Goddess Chandi on the sword of Guru Hargobind (c.1635 CE). This sword was apparently used in the battle against Painda Khan (The sword is now hosted in The Sikh Museum)
Guru Tegh Bahadur visited the holy Triveni at Prayaga in 1662 CE. This visit is documented in contemporary Bhat Vahi records. Unlike those unpublished “bhat vahis”, this one was published by Sikh historian Madanjit Kaur in Proceedings of the Indian History Congress in 1978.
This Bhat Vahi was signed by Guru Tegh Bahadur. The content of the letter is particularly striking. Guru Tegh Bahadur calls himself a devotee of Naina Devi. Note that he does not mention Akal Purakh or Waheguru. In the record, Guru Tegh Bahadur identifies himself as Sodhi Khatri by Varna and Kaushish by gotra. This is exactly how the followers of orthodox Hinduism identify themselves to this date.
Further, Guru Tegh Bahadur appoints a brahmin purohit named Bhoj Raj. He orders Sodhi's of his line and all his Sikh followers to obey the aforementioned Brahmin Purohit. This practice of appointing purohits is just what is referred to by some people as “Brahmanical Hinduism”.
Kavi Santokh Singh's Sri Guru Pratap Suraj Granth preserves a very rare passage that throws light on what Guru Tegh Bahadur uttered in Mughal court. When the Guru was offered the choice of Islam or dεath in the Mughal court, this is what he said, “I believe my Hindu Dharma to be most superior. How can I abandon that which is most dear to me? Which gives so much happiness in this world & that, Life is nothing before honor.”
Finally, the Guru's own passages preserved in Guru Granth Sahib corroborate that the Guru was every inch a Hindu. He says- “This is the blessing of Vedas and Puranas, that you may meditate in the name of Hari”. In the English, translation, many online sources change ਹਰਿ to Lord.
The second painting is housed in Lahore Museum (Acc. No. F-47)
In 1628 AD, Guru Hargobind Singh visited Raja Kalyan Chand at his capital Kot-Kehloor. Rajahim patronage and gifted him the village of Kiratpur and Kalyanpur as Jagir. The Mughal Emperor Jahangir took objection to these relations between Raja and Guruji and asked Raja to remove Guru from the hill state of Kehloor. But Raja refused the emperor’s wish. Raja Kalyan Chand shifted his capital from Kot-Kehloor to Sunhani (Bilaspur). Guru Gobind was taught Shastra Vidya by Rao Bajjar Singh Rathore. Guru Gobind's kids were taught by Rai Alam Singh Chauhan. He was saved at Chamkaur and given protection by Ghorewaha Kachwaha Rajputs. He made his Sikhs model the Rajput culture and uplifted them by making them adopt the Rajput culture including dressing syle. His father and wife were saved by Jaipur kachwahas. He stayed under protection at Raipur rani, Ramgarh, and Chamba, Rajput ruled areas. His greatest general was Bachitar Singh Minhas. His sons' killings were avenged by a Rajput Banda Vairagi. The most prominent victories of Sikhs got, was either under the command of Banda a Hindu Rajput or against divided Afghans who could never muster a large number of horsemen. The decline of the Mughals, Nadir's invasion gave Sikhs their chance which they exploited.
Khalistan was first demanded in 1931. Indira was then just a schoolkid. In 1931, VS Bhatti of Akali Dal demanded Khalistan or Sikhistan with Ludhiana, Jalandhar, Amritsar, Rohtak, Ambala, and Shimla hill states. This was before the independence of India. Bhindranwale did not start the Khalistan movement. Khalistan movement existed long before Bhindranwale was born. Regarding the claim that Indira “rejuvenated” the Khalistan movement, this is also false. The Khalistan movement was already in swing. In 1969, Punjab's ex-deputy speaker Jagjeet Singh Chauhan was campaigning in the UK for Khalistan. Bhindranwale was nowhere in the picture at that time.
What Indira Gandhi did was use the Khalistan sentiment to her political benefit. Because Akalis started the Punjabi Suba movement and were riding on separatist sentiments, Indira propped Bhindranwale who was even more extreme than Akalis. Yes, by encouraging someone like Bhindranwale, Indira had an undeniable role in encouraging the Khalistan movement the price for which she paid with her own life. But Indira neither created nor rejuvenated Khalistan. She tried to use the Khalistan sentiment for her political benefit. Thus, Indira encouraged one separatist to put another separatist in place. This is a very common tactic governments use to suppress separatist movements.
Revisionist Sikhs are presenting as if it was Hindus who were out to kill Sikhs. The fact of the matter is that the first Bhindrewala killed Sikhs as well as Hindus in large numbers. And the anti-Sikh riots of 1984 after Indira's murder by her Sikh bodyguards were a Congress mob. Even Khuswant Singh wrote that BJP and RSS tried to save them.