The word "Sanatan" = traditional
Pro-Sanatan Sikhi people believe that their version or account of Sikhi is the true account of Sikhi which differs to "modern" sikhi.
History Timeline:
SINGHS LEAVE VILLAGE AND HOMES
After the fall of Shaheed Baba Banda Singh Bahadar's Khaalsa Raaj, the Singhs were persecuted. The Mughal policy became such that there was a price put on the heads of Sikhs.
Therefore, the Sikhs left their villages, gurdwaras, cities and homes, and fled to the jungles and desert lands for safety. This was done in order for the survival of the Sikh nation.
The Gurdwaras were given to the "Mahants" to look after and take care of. THe "Mahants" were Hindus, who were generally Keshdhari.
THE MAHANT ERA - Sanatan Sikhi takes birth
The Mahants relied on people to donate food to them and offer offerings. However, they needed a mechanism and means to attract (Hindu) people to come to the Gurdwara, so that they could survive and get enough money.
The Mahants became comfortable in the Gurdwaras and realised that Sikhs will not be back for a while. The Gurdwaras were transformed into Mandars and Bipran Ki Reet (Brahmanism) was brought into the House of Guru Nanak.
Portraits of Hindu gods, goddesses, depicting the Gurus and other figures were painted on Gurdwara walls and buildings. The Guru Granth Sahib was made an idol. Aarti was performed of Guru Granth Sahib Ji. Jyots (oil lamps) and Toof (incense) were used ritualistically. The Gurdwaras were made Brahmanised and Sikh practices were engulfed in Brahmanism.
SIKHS COME BACK
The Sikhs came back from the Jungles after two three generations having past. Returning back to the villages and cities they realised that the Mahants were not going to give back the Gurdwara willingly. The Mahants had in fact made the Gurdwaras there private property. Many Sikhs assumed that “Sikhi” seen in the Gurdwaras was Guru Di Sikhi, not realising the Brahman ideological control.
The Singh Sabha Movement was a movement of a group of Sikh intellectuals who studied Gurbaani thoroughly and realised that this “Sanatan” (Mahant) Sikhi was not in correlation with Gurmat (the Guru’s teachings in Gurbaani). The Singh Sabha Movement tried to educate the masses about Bipran Ki Reet and the Brahmanism of Sikhi and also tried to free the Gurdwaras from the clutches of Mahants.
FREEDOM AT LAST OF OUR GURDWARAS
Eventually the Gurdwaras were freed after many peaceful protests, marches and thousands of men and women giving their lives. Examples of these are Jaito Da Morcha, Saka Nankana Sahib, Saka Panja Sahib etc.
In 1920s the keys of Harmandar Sahib, Amritsar were handed back to the Sikhs. Having regained control, the Sikhs white washed and painted over the Sanatan Sikhi paintings depicting Hindu gods and goddesses and depicting the Gurus with Hindu Avtars. Hindu idols which had been installed in the Parkarma (area surrounding the pool) were removed and Gurmat was installed.
SAFE GUARD SIKHI
To safe guard Sikhi, the Sikh scholars, intellectuals and Panthic organisations gathered together and formulated the “Sikh Rehat Maryada” (Sikh code of conduct) which was passed and approved by Sri Akaal Takht Sahib. The Sikh Rehat Maryada ensured that Sikhs or Gurdwaras would not fall back in Bipran Ki Reet (Brahmanism) and instead follow the true teachings of our Gurus as found in Guru Granth Sahib, the Bani of Guru Gobind Singh Ji and Bhai Gurdaas Ji’s Vaars.