Communities like Reddit are difficult to replicate in the first place. I love Reddit, but the transphobic, hateful, ignorant comments are surely also made on Reddit as well. Perhaps you see them less because it's less concentrated, as there are so many subs and people.
I think though, that OP here is arguing that monogamy is more a product of society and not biological drive. He uses the example that many humans cheat (and as disgusting as that sounds to YOU, it's ALSO a social construct because there are other cultures which are not monogamous). So it doesn't matter what your personal opinion of the matter is, nobody here is arguing that breaking the social code you've agreed to is morally good.