A prominent gay rights activist was among four men allegedly assaulted by a lone attacker on Oxford Street in central Sydney on Monday night, in what the activist believes was a homophobic hate crime.

Police have charged a 34-year-old male with assault occasioning actual bodily harm in relation the attack on activist Simon Margan - the co-convenor of Community Action on Homophobia - and three other men.

The attack left Mr Margan bleeding on the ground with a severely fractured left eye-socket.Police will allege it was one of four separate assaults by the same man at different locations along the famous party strip.

Mr Margan was treated at St Vincent's Hospital along with another of the alleged victims who suffered bruising and swelling to his left eye.

"I was walking up Oxford Street toward Crown Street when a flying kick just missed my head," Mr Margan said.

"I thought he might have a knife, so I stepped back to call for help. When I turned away to call down the street he kicked me again - hitting me in the eye."

Mr Margan said the same man had made violent homophobic comments toward him a few days earlier as he put up posters promoting a gay rights rally taking place a Sydney Town Hall today.

"Every time I turned around he was there ranting about eradicating gays on Oxford St. It was more full-on than you usually get, so when I saw him on Monday night I was really scared he was going to do something extreme."

The 34-year-old make was denied bail to appear in Central local court on Monday, where police will allege that he was affected by alcohol. They also will present video footage from CCTV cameras on Oxford Street as evidence.

A police media spokesman said that there was "no indication that the men's sexuality was involved[as a motive] in the attack", but Mr Margan said he was in no doubt about his attacker's motive.

He said gay hate crimes were not uncommon on Oxford Street, but were only occasionally reported.

"People seem to think, 'I've been assaulted, I'll just get on with my life'," he said.

"We need people to call these attacks what they are - hate crimes. If people don't report them, then they're not setting an example for the next time it happens and the next time."

The Town Hall rally is part of a nation-wide action calling for marriage equality.