Frederick Giunta entered his plea Tuesday in the October attack at Julius. It occurred at a Manhattan tavern where a 1966 "sip-in" marked an early moment in the gay-rights movement.
The 45-year-old Giunta is expected to receive a 3 1/2-year prison sentence.
His lawyer, Hershel Katz, says Giunta's behavior stemmed from drunkenness, not malice.
Police say the victim was trying to defuse a dispute between Giunta and another customer when Giunta hit the victim in the face and used the epithets.
Giunta also pleaded guilty to attempted robbery for grabbing at a man's wallet at another bar.
