I would agree if McCain had not paid for its development. If he or an agent of his created it, he should completely vet it before he passes it around.
Which is why we need to know who paid for it and how they got it. its the difference between being a responsible citizen and perhaps criminal action... certainly libel and slander.
Why do we need to know? If we don't need to know Trump's tax records (as Trump so nicely put it, claiming suddenly the public has no more interest in his tax records other than the rigged media) then we also do not need to fact check the dirt on him that is unearthed. Everything else is hypocritical.