If you remove downvotes you remove the recourse users have to push down bad content. A bad post with 100 upvotes and 500 potential downvotes should never see the light of day because the community decided it’s a bad post. But because no one can push it down and there isn’t enough content to push up over it, now a bad post 10 people would have seen and pushed out of the system is now bothering well over 500 more people because you couldn’t downvote it.