Your argument is much the same as "what happens if juries are unconvinced by the prosecution that the bad-guy is bad and let the guilty go?" with the 'solution' of forcing them to convict of breaking a law even in the case where that law is itself contrary to the [supposedly higher] law that is the Constitution.
The answer is the same: it is inherent in the position that they have the ability to decide. (Whether guilty/not-guilty in a juror's case or for whom to vote in the delegate's.) Anything which allows the arbitrary removal from such positions, and make no mistake the rule proposed is arbitrary, ought to be fought.
Indeed this is directly analogous to a juror prerequisite abrogating the powers of nullification (have you read some of the documentation you sign to be a juror?); nullification is something many courts try to sweep under the rug and keep out of the general knowledge. Why? Because nullification is the power of the jury to judge the law itself, and as that is where the courts gain their powers it is relinquishing power to have to submit to a jury's nullification.
The jurors are picked to have an opinion. As much as I hate it, the people voted for Romney. I don’t know why this is so hard. If it were the opposite like I described, you would probably be the first one on the rooftop screaming that they didn’t listen to what we picked at the polls. What’s the point of polls if they can choose for themselves?