Both of you had too lofty dreams for social media. Reddit itself used to be like that too, by convincing themselves that this sort of idealistic attitude could last, or that “circlejerk”, that is, the influence of majority opinion, was ever not present. This is a place for discussion among regular people, not a philosophical symposium of specialists, as if those environments were truly neutral and universally accepting either.
As platforms grow beyond the most invested niche users, most people will not put more energy into any discussion than a general agree or disagree. The tendency of downvotes is always to become a disagree button, no matter how much one might insist otherwise. In such a semi-anonymous platform, a modicum of politeness is already an achievement.
Really, if you do want to have such a perfectly open and supportive discussion group you might want to select particular people to create a small forum. But by doing that, it’s pretty much guaranteed that you won’t escape some form of circlejerk.