No, on smaller subreddits the downvote button also enforces conformity and a right opinion. You can be as polite as you can, as decent as a scholar, but if your opinion is wrong, you will get downvoted -- and once you get to minus 1, minus 2, chances are other people will downvote you, out of sheer reflex: opinion bad --> already in negative --> here, have another downvote.

It's easier, a thousand times easier, to use the downvote button to express disagreement than to actual type words and construct arguments, and that's how most people will use it.

And I suppose sometimes it can filter the toxic, inflammatory or misleading comment.