Me, I'd nominate hardcore Calvinists.

Not unlikely as to their temperaments, but in terms of their (our) professed doctrine. Calvinists (claim that we) believe in a big mighty sovereign God, and a small weak dependent creature-man. We believe that the human heart is depraved, dead, rebellious. We believe the heart can only be changed by a mighty act of the sovereign grace of God, an act so radical that it is more like resurrection than plastic surgery or a makeover.
AND YET....
I've already once been compelled to go on at great length when razor-brained wordmaster Doug Wilson immediately and eo ipso blamed Todd Palin for Bristol's sexual immorality. Daughter sinned, blame Dad. Boom!
And now that good man has done it again (I infer from the title) and again (check my comments for the remark I target).
In both cases, if you're interested, I'll refer you to my remarks in the comment threads. What never ceases to amaze me (besides the position itself) is the argument (and kinds of argument) I get for — to my mind — pointing out the Biblically-obvious.
I'll close by quoting, well, myself from the second meta:
If I may ask it, ponder that last paragraph in particular.I think it is a pan-Biblical verity that you can never be assured of drawing a straight line between cause and effect in relationships. God has a human son (Luke 3:38) who sins in spite of perfect fathering, who has a son who is saved in spite of imperfect fathering. There's your template.
My great task — whether as a husband, father, pastor, friend or neighbor — is to trust and obey. I will be judged for that, and not for what others do in response to that.
If God did not use means, the Proverbial charges to me as a father would be meaningless. If means were sovereignly effective, the charges to my son to heed, listen, receive, memorize, learn and obey would be equally meaningless.
I still note that God has no grandchildren. I still note that "faith comes by hearing, and hearing by the word of Christ" (Romans 10:17) — not "by the word of Christ skillfully applied by techniques you can read about in my books."
I think many Christians go into parenting thinking a particular formula will yield particular results. Then life actually happens, field work doesn't quite fall into line with that nifty parenting book they read, and they wise up.
But, apparently, not all of them do.
God help the heartbroken mother or father — well, especially father — with an apostate child, who limps over to such a Christian for encouragement and help. Heaven only will tell the full tale of destruction this line of thinking has done to individuals... and marriages ("Yes, that's right, Mrs. ____; if your husband had been a better father, this wouldn't have happened, and your heart wouldn't be in a billion pieces!")
Theology has practical implications. Bad theology has terrible practical implications.
I really would have expected hardcore Calvinists to figure that one out, too.