Why is it always the people of deeply held faith that are asked to "compromise"?

I was listening to Sean Hannity's show today and there was a great deal of discussion of the interview that he did last week with Dr. James Dobson. This is the one where Dr. Dobson said that he and a large number of Evangelical leaders would back a third-party candidate if Rudolph Giuliani was the Republican nominee. Hannity and most of his callers made the point that if enough Christian conservatives either sit out the election or back a third-party candidate that they will be responsible for putting Hillary Clinton in the White House. Hannity said that a vote for a third-party was "half a vote for Hillary".

Yesterday I put up a post called "A question for Giuliani supporters" where I actually asked two questions. One was:

If Rudolph Giuliani knows going into the general election that his presence at the top of the ticket will spit the Republican Party enough to guarantee a Democrat victory and he still chooses to run does that tell us anything about his character?

And the other was:

Is it worth voting for him in the primary when you know he can't win the general?

I repeat the questions here because what I'm hearing here and on the radio and on other blogs is the sentiment that if enough Christians fail to vote for Giuliani that they will bear all the blame for putting Hillary in the White House. What I want to do is turn the question around. If Rudolph Giuliani continues to run and gains the nomination knowing that his presence on the ticket will be so divisive the it will hand the election to Hillary does he share none of the blame?

If enough Republican primary voters insist on voting for Giuliani even though they know that it will split off enough voters from the party to kill any chance of victory do they share none of the blame?

It is though a woman tells a man in plain and simple words that she will under no circumstances marry him if he takes the job in Chicago and he takes the job in Chicago and spends the rest of his life bitching about how she ruined their chance at marital bliss.

Here's another question to the Giuliani supporters who insist that it is the bound duty of every registered Republican to support the Republican nominee no matter who it is. If you are telling the truth about the way you feel then you will support Fred or Mitt if they win the primary and become the nominee. So instead of insisting that committed Christians do what would, to them, amount to selling out their faith and turning their backs upon God why don't you compromise?

What I mean is that everybody seems to be proceeding on the assumption that Giuliani is not a free moral agent. That having entered the race he must see it through and that the primary voters who favor him have no capability of adjusting their choice based upon the likely consequences for the party. Why must those things be so? Why is the onus of responsibility not on Giuliani to step aside or upon his supporters to find another choice in light of the fact that he is utterly unacceptable to too may people?