i find this very satisfying: gently disagreeing with them via a short single positive message like "gay people do deserve respect", then letting them throw a very lengthy, time-invested tantrum before gently and completely disagreeing with their comment with another short sentence, over and over until they get tired.
i find that both very funny and I'm putting out positive messages that negate their bigotry without too much time or effort.
that's just if you have the time and inclination to engage, you aren't morally obligated to subject yourself to abusive behavior.
if it's real bad, they're probably violating a rule, and reporting them will get them banned