Martyrdom has always been a proof of the intensity, never of the correctness of a belief.- Arthur Schnitzler
What about the first Christian martyrs? Jesus' disciples were eyewitnesses to his life, death, and resurrection. If his resurrection and some of the stories of his life were fantasies of his disciples, then their martyrdom makes little sense. In their case, wouldn't dying for the cause lend validation to their claims?
Your is precisely the kind of comment I hoped to elicit by posting this quote. Ans yes, if you were called upon to choose between life and denying what you knew to be true, I suspect you would, however reluctantly, opt for death. And I say that as a devout coward.