One thing I missed that my dad pointed out:
Who is to say that what I see as a mistake was actually a mistake?
Especially given the nature of continuing modern revelation. Just because a policy or doctrine or script or whatever got changed doesn't mean it was wrong when it started. Sometimes it just means the world changed.
Just because I disagree with or don't understand something, historical or present, doesn't mean it's a mistake or ever was. (It might have been; but it might not have been. Tim pointed out nobody has ever claimed the priesthood ban itself was a mistake. They only have clarified that the folk doctrines that sprung up to explain it were mistakes. So perhaps the priesthood ban was not a mistake--and the history and words of prophets who tried to end it and were told not to would bear this out. Perhaps there was something going on in the world at that time that made it a policy God wanted for a short time, just like He wanted polygamy for a short time. It doesn't mean polygamy was a mistake that it got cancelled eventually. It only means that God had finished whatever work He was doing with it.)
Also, I really feel strongly that it's worth repeating: claiming the prophets are human and fallible and therefore we don't HAVE to follow them assumes that while they are human and fallible and make mistakes, we are human but infallible and never make mistakes.
And that is the most ridiculous thing I've ever heard.