Then why do you get points for interacting?
It encourages good content from people.
If upvoting a snarky comment keeps someone from posting a mean reply HN is better for that, too.
People can vote however they damn well please without anyone shoulding upon them. Votes are an expression of something, whatever that something is is properly in the hands of the voter.
(What's the difference between thinking a comment is "wrong" and disagreeing with it?)