> "I don't agree with this opinion so I will downvote this comment"
If that bothers you, then HN is not the site for you. Downvotes for disagreeing has received the thumb of approval from PG[0]. Upvotes are for agree and downvotes are for disagree. On reddit people like to pretend otherwise (even though it's true in practice there as well), but here on HN there are no bones about it.
[0] one example: https://news.ycombinator.com/item?id=658683