^You'd be surprised. Even cops who do their jobs to the letter get blamed and scapegoated a lot of times for things that go wrong. And things will go wrong, in that kind of business.
Basically what you have to understand about the MU's logic post-Stamford is that it wasn't very logical. They were grieving, they were angry, they were fearful and paranoid, and they wanted someone other than "just another random supervillain" to blame for a disaster of this magnitude. Add to this the fact that the Marvel universe public generally has a very reactionary and biased attitude against superpowered beings in the first place, heroes or not, and it's not hard to see where the angry mobs and the mass protests would begin. I mean, this is the exact same public who thought that lynching mutants in public and hunting them down with giant robots was perfectly acceptable just a few years back.
Yes, logically Nitro blew up Stamford and should be public enemy number one. I agree with you; Nitro was the one who exploded and the NW were the ones trying to stop him explode, that's really what it boils down to at its core...but you try telling that to the grieving mothers who have just found out that maybe if the New Warriors weren't so overconfident and maybe if they weren't chasing reality TV ratings and tackling villains out of their league, maybe three hundred people would still be alive. Nitro was evil. The New Warriors were irresponsible. In this situation, the collective minds of the public chose to interpret "irresponsible" as the bigger threat to crucify.