I'm totally puzzled at the negative response to 3bodyproblem. It seems reasonable to say that cucumbers, anuses, mouths, etc. are desirable because we're programed to want penile-vaginal sex, because if we didn't we wouldn't have reproduced, and therefore things which feel like that kind of sex are also desirable. I mean, that seems to be evolutionary theory 101. Why is it not obvious?
And so "normal" is shorthand for the most direct route to reproduction, which is the main thing that's necessary to continue a species.
The further one gets from imitating penile-vaginal sex, the harder it is to understand the immediate evolutionary benefit, and thus there's more need for discussion, research, etc. on those topics, whether it's homosexuality, foot fetishes, whatever. (geez, how do you write this without a zillion double entendres?

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And there are also things that make a lot of people cringe when they see or think about others doing it. Self-mutilation, eating something really gross, etc. The whole carnival geek industry is built on it, just like the whole carnival
ride industry is built on fear of injury or heights or similar things. It's widespread to be grossed out by some things that
other people do, or even just thinking about things that other people might do (eyeball sliced with a razorblade for example), so I don't see the point in criticizing someone for having that trait.
What if this whole conversation were about pedophilia rather than homosexuality? One could make an evolutionary case that men having sex with women as soon as they're old enough to reproduce, say 11 or 12 in a lot of cases, is as much within the range of "normal," (leading directly to reproduction) than homosexuality. Yet I doubt that anyone here would be willing to step forward and make a case that sex with 12 year olds should be widely accepted in society today.
Yes, I believe we need to jump on what appears to be intolerance to homosexuality, and also to jump on what appears to be any tolerance of pedophilia, from a current social standpoint. But those are legal-moral constructs that change from society to society faster than we could possibly evolve. They're just a blip on the long, long timeline of evolution.
So why can't one say that anything obviously aiming toward reproduction is "normal" including pedophilia with children old enough to reproduce, and anything not obviously explicable in terms of reproduction deviates from that norm?
That would make mating displays normal, pedophilia normal, heterosexual sex with women after menopause deviant, anal sex deviant, and so forth. Yes, it seems strange to us, and is not really helpful in passing laws or deciding who to ostracize, but it seems to me to be a perfectly logical starting point for figuring out what other things help reproduce the species directly (gay uncles maybe) or merely imitate the "normal" things (oral sex maybe), from an evolutionary standpoint.