On Reddit, up/down was intended to be used as relevant or not relevant. Then Facebook came around with the Like button and changed the standard.

Coming from the perspective of Digg, Reddit was about sharing external content and giving something an upvote was used to promote that content while a downvote was used to discourage that content from being seen. It was democratic in that the users were relied on for ranking posts without the need for moderators having to establish rules and remove things.

Then Reddit employed an algorithm and most people visit Popular and All making it a shitstorm of irrelevance. People upvote stuff they like that has absolutely no reason to be posted in a sub. Never mind everything that's gone on with Reddit in recent months, it's users' inability to properly use the upvote / downvote buttons that has caused the site to become absolute trash.

Here, we have the added tool of the Star to indicate that we like something while at the same time downvoting it because it's not relevant to the sub. The problem is that the vast majority of people don't want to think about or put any effort into anything. At this point, anything that looks like a thumbs up is getting selected because they like it.

If you disagree with someone, you shouldn't do anything unless you have something to say. Engage with them in conversation and express your point of view - this is "social media". If others feel your point is relevant you should get an upvote; if you're off topic you should get a downvote.

Reading over the other comments here, I think most people are expressing a similar perspective. It's about rankings, not feelings.