Interesting point, and something I've thought about a bit. I think the majority of people who would take the time to write a comment in disagreement think to themselves, why would I post a comment on this post when I could go find someone I agree with that would more likely upvote me, and definitely wouldn't become an enemy. But without opposing views its hard to have a good conversation, so I think people need to have the courage to still speak their mind, as long as it's done in a respectful manner. It's the same with downvotes, there is no reward and puts you at risk of making enemies or people downvoting your content because "you did it first."

PS. Are you on a poker team?