In general, it's wrong for defeated primary candidates to refuse to endorse their opponents. Many "moderates" have been incredibly selfish and sore losers. Murkowski and Crist are the most extreme examples.
Unfortunately, it appears that Delaware could the exception.
O'Donnell's admission that she dabbled in witchcraft (!) is damaging enough to her credibility, although one could argue that she was young at the time and has since atoned.
No, what is worse is that in the same interview, she claimed that it was morally wrong to lie to a Nazi about where a Jewish child is hiding. I'm sorry, but that is just beyond the pale.
Yes, Lying is generally immoral, sinful and wrong.
But there are worse things. Murder is one of them. Telling a Nazi where a Jewish child is makes you an accessory to murder.
Judaism is the religion with which I have the most familiarity; one of its teachings, called pikuach nefesh, is that when a life is at risk, one can break almost any other commandment (short of murder, rape or idolatry) to save it. I'm sure that most Christians would agree with this. No reasonable person would say that it is better to become complicit in murder than to tell one lie.
There may be gray areas - what if one is unsure that someone will die? But in the scenario given to her, her answer was obviously wrong.
Better to have a moderate without principles than a 'conservative' who endorses complicity in murder. O'Donnell should do the honorable thing and stand down as Republican nominee. Castle may, unfortunately, have been right to withhold his endorsement - I could not in good faith support a candidate whose conceptions of morality are so distorted as to be an embarrassment to all people holding conservative views.