The whole piece should be a must read, but this point cannot be stated enough in the coming months:
If everyone must choose between two evils, we should hesitate to declare others evil simply for making a choice. Each person must draw his own red lines. But classifying an issue as one on which reasonable people cannot disagree—shifting to the rhetoric of moral judgment—is hard to reverse. At the outset of a campaign where so many reasonable people are poised to disagree, it seems unwise.