I don't particularly think so. What matters is whether the stuff in the book was true, not whether the author is of unassailable character

When one's goal is to look for any reason to downplay facts, questioning the character of the messenger is a standard tactic.

Indeed it is. One can't help but wonder why such a well-known distraction tactic still remains so effective against so many

Could be courage guided by a paycheck. Would not be surprised if the publisher did not reach out directly to suggest writing a book.