I've never said or implied that a parent is not responsible for their children.
That statement makes it obvious that you have not raised a teenager. They have minds of their own and will do what they know is best. After all, their few years on this earth and the vast knowledge they have accumulated trumps their parents teachings. 
To say that all teenagers will do what they will regardless of their parents wishes is an over-generalization. Many, if not most, teens will listen to their parents and do as they wish - be it out of fear, respect, or responsibility. That is, if they were raised that way.
No one is suggesting Sarah Palin was helpless. No parent has control of a teen aged child once that child steps out the door. When they step out the door you are trusting that they will adhere to what you have taught them in the past and that they will exercise good judgment. However, our children, like us, are not perfect and they make mistakes.
A parent should be able to evaluate whether their teen is rebellious or irresponsible. That parent should not let that teen walk out the door. That parent should exert the control over their child that they rightfully can. Evaluate the situation, take control as your power allows. She should have done this, and done what was right.
Palin may one day person need to make dire decisions affecting matters of national security. This would be based on her ability to evaluate situations comprised of very complicated factors. A person requiring that ability to scrutinize should at the very least be able to evaluate their own child.
Now, I don't think that this alone disqualifies her for the position. It certainly does not help. I hope for her sake that there are not too many more examples of her being a weak airhead.
To suggest that Sarah Palin can't control her daughter simply because she got pregnant is grasping at straws.
Though it may not prove it beyond a doubt, it certainly is an indicator. It's not a straw, it's a solid brick in what could be a larger foundation.
