To be fair, the other guy started it by throwing around the term gαy.
The former was not directing the term to the poster, but commenting on the gαyness of the video (which in addition to being stupid, is completely secular and irrelevant to anything Catholic).
The second fellow, offended that his secular video was not appreciated, escalated the matter, and intentionally directed an insult to the first guy.
Would you believe it is not necessarily a sin to criticize a video, but it is to deliberately insult someone, even on a forum?