Cliff May wrote a post on National Review's The Corner group blog that contained a brief note complaining about how hard it is to immigrate to Brazil. I wrote him a brief note explaining why that was the case (as it turns out, he knew this): Brazil has a law that states that whatever Brazilian citizens have to go through to get to a given country, that country's citizens have to go through to get into Brazil. Cliff pointed out in his personal reply, quite sensibly, that Brazil has nothing near the security considerations that the US does, and therefore it can rightly be considered a rather childish tit-for-tat response.
All this is well and good, but here is where I develop a great deal of respect for Mr May: I responded (still correctly) that if security were our reason for implementing those measures, then we needed to take another look at them, because they were (by and large) ineffective at accomplishing the stated goal. Instead of getting tied up in what had become a rather off-topic rant (I tend to get a bit... animated... when it's a subject I care about), he simply (and politely) responded something to the effect of, "Good points."
I wish I had been as courteous in my emails to him.
A similar event occurred earlier, when a now-departed talk show in Denver was hosting a show on the Columbia disaster, and I called to mention that some friends of mine had done the math and proved there was no way it could have gotten to the International Space Station, and that even if they had, it would have condemned them to a slow death instead of a quick one, as we couldn't have rescued them in time anyway. The problem was, all I had was my friends' word on it, and there was no reason for the host to trust them, even if I did. He very deftly let me speak my piece, and then moved on. I can't convey (it's been so long) how classily he did so, but let me assure you that it was very well-handled. This is why I don't get paid to do stuff like that-- I would have gotten into an argument, rather than handled a crank (which is all I was, to him) politely, and moved on.