The misbehavior of Facebook has been well documented and has been going on for many years. Facebook has been shifty and deceptive in their responses, and there is literally no reason to give them the benefit of any doubt at this point.
Your comments about hard data are well-taken, but you talk as if we have no, or very little, evidence that harm has been (and continues to be) done. I think that we have a lot of evidence to indicate that there's a real problem here -- and one that Facebook continues to downplay. None of that evidence is as clear-cut and solid as physical injury is, but that's to be expected with social harm.
> Why, in this case, do we seem eager to throw scientific rigor and frankly due process out the window?
I'm not eager for that at all. On the other hand, the evidence we do have very strongly indicates (but does not prove) that there's a real, serious issue here. Are you suggesting that we should ignore that? If we waited until there was zero uncertainty on things before taking action, the world would be unacceptably dangerous.
Facebook could have helped on this front by being honest and taking the issue as seriously as they take profit-generation. But they chose not to, and now, after so many years of deceptive and abusive behavior, we have no reason to trust them anyway.