It's tempting to define "impoliteness" as disagreement with progressive beliefs about feminism or white racial guilt. Judging by what Scalzi has banned people for, he seems to fall victim to this. He uses the banhammer more than any other blogger I've followed. The others don't feel the need to curate the discussion so closely.
It's fine to be so closed off in your personal space, but the intellectual air can get a bit musty.
Do you have some examples of him banning people who were behaving well and discussing topics respectfully but were still banned? I actually don't see him banning many people; I think he's just frank about being willing to ban.
In particular, I think a lot of my fellow white males who charge into topics of sexism and racism do so without significant respect for the lived experience of participants or the large amount of existing discussion. It is easy for them to see a ban on that behavior as intolerance of their opinion.
One blogger I'm fond of recently quoted this bit: "The more foreign the idea, the more relational groundwork you need to do before you can broach that topic." [1] He was quoting a Christian pastor who is talking about how to introduce the notion of human evolution to Christians who are (incorrectly) hostile to it. But it applies anywhere: jumping in and expecting people to instantly listen to your views is in itself a behavior, and a lot of communities find it disrespectful. That it isn't intended that way doesn't really matter; part of being respectful to people is caring about whether your friendly intentions are matched by the impact they have on your audience.
Well next I see a progressive, I'll let them know that some anonymous internet guy is keeping a list. I'm sure they'll be impressed.
In the meantime, you might think upon respect a little. It turns out it's not just a far-left thing. If a liberal walks into the middle of a conservative talk and starts shouting slogans, people in the audience aren't just going to say, "Hey, tell us more, stranger, about your novel views." They're going to shout him down and throw him out, because his behavior is disrespectful to the existing audience and dialog.
The difference between you and that liberal is that the liberal will know that he's protesting, not trying to participate in a discussion.
I understand you want it to be magically different for you online. Which, hey, it's nice to have unrealistic dreams sometimes: it adds some spice to life. But if you actually want to start influencing other people's views, rather than just have the satisfaction of vomiting your notions and upsetting people you didn't really like anyhow, then you're going to have to work on on demonstrating respect for the people and the existing discussion, something they were building before you turned up.
It's fine to be so closed off in your personal space, but the intellectual air can get a bit musty.