>I can be upset and angry and still participate in a rational discussion.
The problem is that it would only take a few people who can't remain rational for a tipping point to be reached whereby the overall quality of debate badly degrades. (That's when some of the most valuable contributors start to disappear.)
>What will we do when an issue is both important and divisive
If such a political issue affected hackers directly then there'd be no way to avoid that discussion.
>Do we want to prevent, to silence, discussion?
Of course not. And that's precisely why politics in general should be avoided.
Aside from the eve psych, I'm with Eliezer Yudkowsky on this: