I sort of agree with you in that I think the highest quality of commenters won't be super squicked out by either horse sex or talking about cranial capacity differences between races or whether a trolley should run over 3 babies or 2 toddlers. But that's too high a bar! I think plenty of people are disgusted by certain topics and it's worth acknowledging that even smart, mostly well reasoned commenters can be scared away or simply feel unwelcome. Reddit can be a home to various mutually hating subgroups because of its structure, but we use a much less divided system and it's worth considering what topics attract what sorts of commenters.

Plus I don't actually want to talk about horse sex all the time as a filter.