Constant Reader hilzoy made a post in comments which I liked so much that I'm putting it up here as a post of its very own. I've gussied up the layout a bit, but made no other changes.
About civility: I think C. S. Lewis gets it right.
The real test is this. Suppose one reads a story of filthy atrocities in the paper. Then suppose that something turns up suggesting that the story might not be quite true, or not quite so bad as it was made out. Is one's first feeling, 'Thank God, even they aren't quite so bad as that,' or is it a feeling of disappointment, and even a determination to cling to the first story for the sheer pleasure of thinking your enemies are as bad as possible? If it is the second then it is, I am afraid, the first step in a process which, if followed to the end, will make us into devils. (Mere Christianity, p. 106)
I think that if one really tries to live by this, one will be inclined to say many fewer harsh things, and those one does say will in general not be said in a way that is needlessly divisive. And if one is aware that really trying to be charitable does not ensure success, then one will also think hard before saying harsh things, in order to be sure that one does not allow oneself to be motivated by the desire to think ill of one's opponents. One will also try to see even really bad people as both comprehensible and redeemable, and if one is in a position to do so, one will try to reach out to them. And one will take seriously the possibility that one is mistaken about them, and even hope that one is.
That being said, I don't think that the answer is not to speculate about people's motives or character. I think I should try to be charitable, to consider seriously the possibility that I am wrong, and to express myself in a way that leaves that possibility open. But I also think that the character of our leaders in particular is extremely important, and that it would not serve us well to stop thinking about this. Moreover, I think that we have enough information to draw some conclusions about their character, and that we can also speculate where we lack conclusive evidence, as long as we are clear that that is what we are doing. But we should always try to remember that politicians are people like everyone else, as liable to confusion and weakness as the rest of us, and that it is no more permissible to say hateful things about them for the hell of it, than it would be to do this to someone we actually know.
At least, that's what I think.