I love Kerala. A place of unearthly beauty and tranquillity, contrasted against the chaos and noise of the towns. But that's India, I guess.
And yes, a superb place for bird-watching. I admire the majesty of a crane, the swift grace of a swallow, and I do love a cockatoo. I am sure we are singing the same happy song here.
Gender preference doesn't mean gender choice. It's not something you can change by going to the barber or the priest, or even the surgeon.
And it isn't usually something people make a big song and dance about, especially if they are seen as a minority, or somehow abnormal. They hide their orientation for fear of exactly the same sort of hostility and embarrassment you mention.
Step into his mind for a little. How does he know whether a stranger is gay or not? No outward signs, no badges nor affectation of dress.
Unless one is in a safe environment, LGBT+ folk don't advertise their orientation. You weren't displaying any overt signs of your own inner desires, were you? No browsing through a gentleman's picture magazine, no leering at the teenage schoolgirls, I trust?
There must have been something about you that said to this chap, hmmm, I might be in with a chance here.
Obviously he made a mistake with you. We all make mistakes, and when it comes to sex, they may be truly epic disasters. I have tales I could tell that would not just curl your toes, but bend you into a pretzel shape.
Which, as it happens, is part of one of my stories, but I'll save that for another day.
May I suggest, that if something like this happens again, you treat the fellow with the same politeness and discretion he displayed? All you need do is say, "Oh, I am sorry, you have picked the wrong man. I don't do that sort of thing anymore. Doctor's orders, you understand, maybe once the infection has cleared up?"
There's always some way to be sweet and polite and saying no. Most women are pretty good at it, through years of practice.
Of course, if he persists, then a swift sock in the teeth can work wonders, but again, most women opt for a less physical demonstration. Changing seats sends a clear message without the risk of engaging in a vulgar brawl.