One of the most common talking points that I hear from people who are advocates of leather, especially those who work within fashion, is that leather is simply a byproduct of the meat industry. The claim that it is simply a by-product of the animal agriculture industry is used as their justification to buy leather products because they think that they're just the waste of the meat industry and that they are up-cycling material that would otherwise be thrown away. What these proponents of leather never address though is that these so called "by-products" are just another way in which the meat industry profits and that leather would not exist in the first place if it weren't for the raising and butchering of animals! Like I am genuinely baffled that people believe that the meat industry doesn't proliferate its existence through the selling of things like animal skin and the other remains that aren't flesh. Of course this doesn't even touch on the environmental impact required to produce leather, which includes that of the meat industry that raises the animals (which has a horrific impact already) plus the additional awful production practices like chrome tanning that are extremely common in the leather making process.
Also, a thing that especially irritates me in the TikTok video that I linked is the creator equating faux leather with plastic leather or pleather, when faux leather encompasses more than just pleather and contains leather alternatives that aren't made from plastic! That seems like something you should know as someone whose job requires a large knowledge of textiles/materials but I guess he for whatever reason doesn't know that or at least doesn't mention it
Also leather is just fucking uncomfortable lol. When I was a teenager I bought a leather jacket because it was COOL, but holy fuck it was so uncomfortable, I was usually sweating and freezing at the same time. Even when it comes to boots (which historically might have been necessarily made of leather to keep ppl's feet dry and warm, idk) we now have much better materials, and crying about microplastics is nothing but carnist cope
Not long after I went vegan, my dad tried to get me in a gotcha about leather, how faux leather is all plastic and REAL LEATHER is so natural and great. But, uh a) I don't use faux leather either, b) something like 95% of the cool real leather is cured with extremely toxic materials and just that pollutes more than any microplastic-laden shitty pleather would. He rebutts with "yeah but you can cure leather traditionally, without chrome, they do that in Italy (or some other country)", but had trouble answering which kind of leather he usually buys, seeing as the cool "enviromentally-friendly" (if you disregard the entire cow mass breeding part) kind is super expensive.