Someone needs to be the fall-guy. The gov't, the people, everyone is now screaming in the after-math for someone to take responsibility. The Gov't and the innocent people won't stand for anything less. They either need someone to take the fall (become the fall-guy) or assume full responsibility for it all happening. Cosmic entity possessed us all to do those evil deeds won't cut it. It rarely does. Sure, the hero's and villains who united to put and end to it all understand, but those outside those groups won't.
Scott knows this and that's why he's allowing himself to be martyred for the cause. It's why he didn't even resist arrest once it was all over with. He's taking one on the chin for all mutant-kind and saying to everyone, "It's my fault, put all the blame on me." So that all the suspicion and blame don't fall on other Mutants unnecessarily.
And when I say that, I mean "Everything they've done with him over the last decade" (well, just over a decade). They turned him into Telepathic Adultery Man, and then into the militant isolationist extremist who became the type of person who'd become New Dark Phoenix, kill people and show no remorse. Trouble is, so many more people like the "new" Cyclops we've had from around 2001 onwards and find him more "interesting" that we'll never, ever get the old one back, outside of this time-travel teenage X-Men shenanigans going on soon.