I always take it to mean that a down vote is supposed to represent that the content of the post was off-topic, misinformed, or otherwise not useful or inappropr

I always take it to mean that a down vote is supposed to represent that the content of the post was off-topic, misinformed, or otherwise not useful or inappropriate. I often up-vote people that I disagree with (or who are disagreeing with me) because they are presenting their argument in a way that is reasonable and intelligent. Ex. I would down-vote someone if they started name-calling, I would not down-vote them if they had an opinion that I thought was wrong. Of course, this would be dependent on how good the argument that they present is, or if the opinion is intentionally flammable.