I don't believe Kanyon was fired for being gay. I do believe rumors of it at the time did him no favors. Gay or straight, he was not someone Vince would push. Granted, this is years ago, but saying Kanyon wasn't any good was a terrible thing to say and was completely untrue.
John Cena on Chris Kanyon's claim that Vince McMahon was homophobic and that he was fired for being gay:
"He came out of the closet after he was fired"
"He wasn't any good"