Sometimes I'll up-vote or ignore these if the "wrong" is really common, and there's a reply with a really thorough and valid debunking or explanation attached, just to avoid burying that reply (which TBH, education should be the proper response to someone being wrong). Can't learn if the education is always buried or hidden before people ever have a chance to find it, after all... Or maybe that's the goal for some down-voters, I suppose?
I down vote only things I find that should not be posted like as-persona or something I really know is just wrong.
Of course there is a bit of blur between something being wrong and something we disagree.