I think this is a massive problem - Your suggestion about collective downvoting pools I think is a good idea, where people could delegate some steempower to such a thing on a regular basis - sort of the opposite of curation.
I don't think people are going to individually get on the flagging - for fear of retaliation, collective, consensus based downvoting seems to be like a sensible solution.
I don't know much (read: anything) about the technicalities of such things, but surely it'd work just like a curation trail, or could we create a 'downvote whale'?
I think there also needs to be some really explicit tightening up of what counts as abuse - so that no one's surprised when then get voted down.
If this platform is going to evolve I think collective curation in general needs to play more of a role - I've been upvoted a couple of times by curie and ocd, and it's a massive boost... the same could work wonders to stop discouragement at the other end!