Although the BHU has backed Mr Khan, he has been unable to take classes.
BHU Chancellor Giridhar Malviya, who is the university founder Madan Mohan Malviya's grandson, on Thursday backed the Muslim professor whose appointment at the Sanskrit department triggered a row, saying had the leader been alive he too would approved.
A day earlier, a section of the students took out a march opposing another group that has been demonstrating against Firoze Khan's appointment.
On Thursday, Congress general secretary Priyanka Gandhi, Rajasthan Chief Minister Ashok Gehlot and BSP Chief Mayawati extended their support to Professor Khan.
Although the BHU has backed Mr Khan, he has been unable to take classes. The protesters say only a Hindu can teach Sanskrit at the university in Varanasi.
BHU Chancellor Justice Girdhar Malviya, retired judge of Allahabad High Court, on Thursday said the agitation against Mr Khan's appointment is wrong.
BHU founder Mahamana Pandit Madan Mohan Malviya had a broad vision. Had he been alive, he would have certainly backed the appointment of Professor Khan in the university''s Sanskrit department, said Justice Malviya.
Taking to Twitter, the Congress leader too defended the appointment.
"Our languages and culture are our speciality, our strength," the Congress leader tweeted.
"Sanskrit language has vastness. The constitution of our country has vastness. Any teacher can teach Sanskrit in a university," the Congress leader added.
Rajasthan chief minister said his Uttar Pradesh counterpart should intervene in the matter.
"I am in touch with the Chief Minister and Deputy Chief Minister of Uttar Pradesh. The issue that has been created about Dr Firoze Khan teaching Sanskrit in the BHU should be resolved soon. The Chief Minister and Deputy Chief Minister of Uttar Pradesh should intervene in this matter," Mr Gehlot tweeted.
BSP chief Mayawati also blamed the government for the controversy, saying education and politics of religion or caste cannot be linked.
On Wednesday, a section of students took out a march on the campus in support of Professor Khan, raising slogans in his favour.
"Any one can teach Sanskrit whether he is Muslim, Sikh, Buddhist or Christian," they said.
Meanwhile, ABVP's dharna against Mr Khan's appointment entered the 14th day on Thursday.
Swami Avimukteshwaranand Saraswati, mahant of Vidya Mutt, on Thursday reached the BHU campus and lent his support to the protesting students.