If someone just comes up to someone out of the blue and says they won't have sex with you there's nothing wrong with being angry or telling them to fuck off... I'd do the same if someone came up to me and said that and I'm not trans. The situation in the comic is not about someone's preferences, it's about people who constantly bring up their preference out of the blue for no reason other than to use it as a weapon. You've never experienced that problem, neat, good for you. A lot of trans people do.