Totally agree about the backhanded, off-topic bashing that goes on. A lot of it seems just plain mean spirited. No reason to twist the knife in unrelated topics.
As far as threads being solely for positivity, though, that, to me, is a bit of a "circle jerk" mentality. I'm not saying it's OK to just derail an overall positive thread with nonsense, but on the other hand, some of the criticisms are valid, and impetus for worthwhile discussion, as long as ppl have open minds. Even so, human nature being what it is, requesting that only positive posts be made in an OP is really just an invitation to trolls to infuriate ppl for kicks.
The only way around that is to start thread banning ppl for the simple reason that they do not share the same opinion, and that's a little extreme on any fan forum.