1) Other coins can rollback as well..  will u stop them ? NO ... so topic closed. They have used this "feature" to save the coin.  
2) It was the question to die or not to... They have chosen not to. That's pretty sad uh ? It will hurt POS reputation ? I guess it will save, couse everybody will know
that in such kind of live or die situations, coin will have an opportunity to survive.
3) You don't like crypto's which can rollback ? Why are u BC (POS) holder? Couse you are 101% sure that it won't happen to BC ? Seriously ?
4) That's why they have did that, not to let away thief with 1/3 bag and to fuck up whole coin.
5-6) Yeah - never trust anybody even yourself when u think you are 101% right... so there's no need to talk about the trust of exchanges...