Negative bar experience with ignorant person, but kept my mouth shut. Should I have not?

I feel like shit because I went to a bar last night, BDUBZ, and this guy started talking about how “some gay” was telling him how being gay is genetic, which I personally also believe in a sense but that’s beside the point. He starts ranting about how gays aren’t born that way, says we are mental folks who need some mental help. Then finally directly says gays are mentally ill. I just left, mind you I was really drunk and kept staring at them and they knew and I feel like that’s why they spoke up and further engaged us passively. But I didn’t say anything. I feel like I had some responsibility to say something or stick up for myself but what difference would it have made. I feel like that was an opportunity to inform some ignorant people, but I also would have enjoyed shit talking him. Instead, however, I did nothing and I feel useless.