What they are conveying is that “dude” is clearly not a gender-neutral term, as a straight guy would agree that they “fuck people”, weird as the phrasing is, but not that they “fuck dudes.” It demonstrates that they themselves don’t perceive the social understanding of the term “dude” as gender neutral, not that “fucking dudes” is bad. It could also be used to debate a lesbian by the same token.

In my experience, sexual inferences are the fastest way to educate someone who doesn’t see a word as being gendered, but I can see how what they said could be read as using gay sexual activity in a negative way to someone not reading this thread and skimmed over the rest of the text in that reply.

Playing dumb is used by bigots as a shield to continue their bigotry unimpeded. Not allowing any room for them to play dumb is the only way to reach those kind of people.