Refusing to vote for candidate X, but not challenging his legitimacy, is living with the results.
If a conservative takes his marbles and goes home pouting after this primary, he or she is just, putting it gently, politically stupid.
Not necessarily; let's assume that a full 50% of the Republican party decided, as a matter of principal, they would not vote for anyone supporting exceptions [for rape, incest, etc] in illegalizing abortions... if the GOP consistently lost by promoting anyone who supported the exceptions they'd either (a) quit endorsing such people, (b) such people would keep it on the hush-hush, or (c) the party's relevance would decrease.
The only way you have, for certain, to influence party is by support or non-support; providing support when the party violates your core ideals means that the party has no incentive in regarding your core values: they already have your vote.
A) You don’t elect a president and have his stance on abortion become law.
B) If you really oppose abortion, the smart thing to do is crawl to the polls to vote for Romney.
C) Leaving the army when your general has some views you don’t agree with loses wars. You feel principled but your cause is defeated.
All the reasons for not supporting the winner in the primary against our enemy, I see as really stupid politically. Maybe naive or easily distracted in addition to stupid.