Charles is not -- [ Erik says, but he hesitates almost instantly, because that's not the truth. He remembers a Charles here before, one in a wheelchair, and Erik remembers the bullet shattering Charles' back. It might not be the same as what Tony Stark is referring to, but the implication was there, and the damage was done. ]

He refused to acknowledge that mankind wasn't trying to cheat us. Charles was naive enough to believe that mankind would launch missiles at us and were honest men.

[ His words are deliberate enough that he doesn't take accountability for paralyzing Charles. ]