You certainly did the right thing, though, if you catch them again, question their sexuality in turn. Looking at the situation logically, they're targeting him for being gay, by preferring men to women, he removes himself from competition with women they might want, if they were straight. By being homosexual, he is removing himself from the running, so why the harassment? Truth is, he is now one more bit of competition for them. They're so far in the closet they're finding Daddy's gay porn stash, and now they'll never come out. They don't know it, but deep in their subconscious, what's making them angry about him isn't that he's different, it's that his interests create more competition for their potential mates. If they were truly straight, they'd be thankful for him.
All in all, nicely done.