I disagree completely with you, and I have two examples of other communities where downvotes exist and work well:
It's too bad that it's not possible to take back a downvote on PM, though, like you can on reddit (but not on hacker news; furthermore HN small arrows make it very easy to miss, particularly on touch devices).
I didn't downvote you, because I don't downvote people I disagree with on matters of opinion, and I think it's wrong to downvote you for this. However, downvotes are extremely useful to express the "crowd wisdom" on technically wrong messages. I don't think you to be technically wrong, only misguided.