We should never downvote a comment just because we disagree with it. We should only downvote comments that don't contribute to the discussion. If someone is blatantly wrong, their information could be a common misconception that needs to be addressed and seen by everyone. Comments we disagree with are most often very good additions to the discussion and should be upvoted, even if they're factually inaccurate but there is a comment that corrects them. We have to include more ideas, not filter out the ideas we disagree with -- that creates an echo chamber which helps no one.