but since someone has to address it, let's bullet point
-there's a serious history of straight culture and pederast culture: see child marriage, which is still prevalent in parts of the world (for example, West Virginia, where state lawmakers just blocked - as in, on Wednesday - a bill to ban child marriage) and unlike NAMBLA, practiced openly and without taboo in many of those places. As always, pedophilia is not related to sexual preference, or gender identity. Labeling queer people as deviants trying to recruit children is both the oldest and ugliest smear in the book.
-there is no objective standard of "conforming" sexual practices. Attitudes to both sexual practices and gender identity have varied widely across human societies. This is, as you put it, a sociological fact. So you/anyone can take that "historically deviant" argument as a basis for anything and shove it.
-and since I'm stuck addressing incest: no, I don't have a problem with it if adult siblings on birth control want to fuck each other. The issue isn't sex, or attraction, but that their potential children can't consent to being the product of inbreeding. I might find it weird, but it's their business. And to get the inevitable reductio ad absurdum out of the way: same goes for adult child and parent relationships. I would assume that virtually all parent-child incest begins or takes place when the child is a minor, i.e. molestation which is obviously unacceptable, but in the hypothetical event that an adult was like yeah I want to fuck my dad and we use birth control, go with god. Presumably it would cause difficulties with their relatives and, I mean, many other facets of life but again, that's their business.
I will note that one reason that Republicans shouldn't try biscuit's galaxy brain level incest gambit is that they have a long, long history of actively defending sexual assault and misconduct, as well as pedophilia (see: Roy Moore). So do the Democrats tbc; it's only recently that they've been dragged into more responsible positions by MeToo etc.