Gay, no f*g, yes.
Or just calling someone gay repeatedly, then sure, because it's harassment also, and using it like a slur.
I try to take people using gay as a random buzz word with a grain of salt, because it's as ground into people as any other curse word.
But if they are just vile with it, then it's the same as saying "GG noobs," or "GG f*ckers" or something else like that.
If it were a totally fine game and he just ended it on a stupid comment like that, I would be inclined to pardon unless it were accompanied by other foul behavior.
And, not that it matter, but I'm also gay.