Amar'e Stoudemire -- I'm Sorry for Homophobic Slur

Knicks star Amar'e Stoudemire is owning up to a homophobic message he sent to a fan on Twitter this weekend -- and now wants to publicly apologize, telling TMZ, "I should have known better and there is no excuse."

Amar'e adds, "I am a huge supporter of civil rights for all people. I am disappointed in myself for my statement to a fan."

The NBA just announced ... Amar'e has been fined $50,000 over the incident -- for what the league called "offensive and derogatory language."

Amar'e sent the message Saturday in response to a bitter fan, who criticized Amar'e for the Knicks' poor finish last season. The fan wrote, "@Amareisreal you better come back a lot stronger and quicker to make up for this past season mannnnnn deadasss!!!"

Amar'e responded in a direct message, saying, "F**k you. I don't have to do anything f*g."