Every time I see this argument, I keep thinking... what societies? Which ones? They only ever name a handful and neglect so many others.
It's almost like they built this entire narrative generalizing a diverse collection of cultures based on a preconceived narrative formed only on a handful of examples.
Precisely. Nearly all historical cultures have very rigid gender roles, sexuality, and insistence that you must be straight (heteronormativity or whatever). There may be references to deities in stories having gay lovers and the like (Xopichilli in Aztec mythology is the patron of gay men, Zeus abducting Ganymede), but they're gods and mythic figures. Even in Greek society, actually being gay was heavily stigmatized. If you were bottom, if you sought just men for relationships, you were seen as being womanly and not really a man. If you were a man, you could only fuck men who were slaves and prostitutes, not equals, because it was seen as degrading for someone to be the receiver. A woman wanting to work in a man's role or a man wanting to work in a woman's role? Incredibly rare and, though a few famous stories show that (like Mulan), it was uncommon in reality and usually involved having a lot of power.
SJWs have a very distinct idea that the "noble savage" myth is true, that people who have less access to technology and things like medical knowledge and contact with other peoples are inherently superior morally to everyone else. It's the concept that they're somehow closer to the world and less violent, even though humans have been and always will be varying in terms of morals and will never wholly get along. It's downright hypocritical when you know they bitch whenever the noble savage stereotype comes up in media.
It's also frustrating because it's historical revisionism at its finest. What they end up saying implies that they think the people who thought diseases were caused by magic, curses, and gods, who thought that owning people as property was a perfectly fine thing, who thought the earth was the center of the universe, and so forth, were totally cool with being gay or a woman acting in what they'd consider a man's role or a man acting in what they considered a woman's role? Bullshit.