In the interview it was stated that two signatures are required, so Sonny doesn't have access and can't sign by himself. But that was Sonny's own statement. The question is WHO is it, specifically, that needs to state the answers to these questions, that you trust enough to believe?
I think Rassah has pretty much nailed it. Those who believe leopards don't can't their spots (or at least no in such a short time) are going to believe that Sonny would surround himself with shady people in any new venture and so not take the word of anyone associated with him, so assurances from others involved in BFL are going to be pretty meaningless to them. Those who have absolute faith in BFL aren't going to be convinced otherwise by arguments about Sonny's past transgressions.
People need to decide their own risk tolerance here. Nobody gets a prize for persuading someone to "change sides".