Moral relativism makes me feel extremely weird

The way out is to treat your personal feelings as the truth of the highest instance, so if you feel an act is wrong then it is wrong. The truth is different for every single person, but it doesn't vary much between most people, which is what we call common morality. Eg killing people is bad. Some people disagree with that but that's pretty harmful for our society so we isolate them.
All in all, if you're not a psychopath of some sort then your judgement is sane and pretty close to what most people consider the truth. That's close enough. Too much thinking is harmful for you, leave that to other people, just act in accordance with your principles and don't hang around people with radically different ones

Morality shifts over time. What was immoral at one point might have become moral at another. It also depends on society. 300 years ago the "truth" was that slavery was ok and that blacks were less intelligent, now it's not. People that believed that use d to be right then, and people that don't are right now. There isn't a single Objective Truth ™ out there, because people change, times change, hence their conduct changes too. Maybe in another 100 years being transgender or whatever will become as normalised among everyone, and people will be more open to it than they are now. Simply the definition of "being right" changes because everything around us changes

jesus I just wrote a huge long reply to this and managed to sausage finger the back button and delete it all. FUCK

in short: things generally have a purpose; speaking from a purely materialistic perspective, the purpose of biological things is to reproduce; murder prevents that; murder is bad (your instincts provide an intuitive shortcut to this conclusion). Anybody who ever thought about slavery realised it was bad but they usually lacked capacity to do anything about it, ie. slavery didn't become bad, it was always bad, people just didn't think about it. Objective truth is real; 1+1=2 and that doesn't change; failure to realise that implies a defect in the observer (eg. they're really drunk and are seeing double), not that 1+1=4 that day or whatever.

last question first: because it's what they all do, from viruses to bacteria to fish to squids to dogs to cows to people. Any species that doesn't goes extinct, which you seem to agree is bad.

second question: the total biomass will remain approximately the same; it isn't somehow immoral that it's allocated to our species rather than any other. It's also worth noting that megafauna, ie. us and only us in most areas of the world these days, play an important role in maintaining the ecosystem for other species. See, for example, this TED Talk about elephants:



As such, it's by no means clear that removing humans from the equation will make things better for other species.

first question: 'rights' are a modern (and highly parochial!) concept and are entirely anachronistic in this context. It's also likely that whatever you think happened is grossly exaggerated -- Western European women in the middle ages had plenty of opportunities to be educated, for example (I read Europe in the High Middle Ages by John H. Mundy recently and he was talking about how some Europeans were confident at the time that Islam would be subsumed because Muslim men would all want to get married to Christian women, who could actually hold a conversation, and Muslim women would prefer to marry Christian men since they'd actually be allowed to learn to read etc. LOL). See also eg., Heloise and Hildegard of Bingen.
It might also be worth noting that there were plenty of highly accomplished women that opposed women's suffrage back when that was a thing. Gertrude Bell comes to mind.

Still, I'm being parochial now, so let's talk about, for example, coerced marriages (very typical in hunter-gatherer societies, and seemingly still quite common in the Islamic world), to some extent women benefit from those policies too -- specifically the female relatives of the abductor, who thereby ensure their relative is going to reproduce -- and will usually support the men against recalcitrant females (it's also a good way to get 'divorced' in cases where the wife is dissatisfied with the husband, so in some cases the 'abductee' will arrange to be kidnapped). The dude at traditionsofconflict.com writes about this at some length. This kind of thing occurs in other species as well -- the alpha female of any given chimp troop will, apparently, help her son(s) pester other monkeys into having sex with him.
Note that I'm not saying any of this is morally good, and in fact I picked this specific example because it was both commonplace and something I find repellent, just that women have benefitted from and have supported the 'patriarchy' for their own reasons.

Are you just going to ignore first wave and second wave feminism movement that happened prior?