My meanness can, I think, be traced in part to my attempting to inch closer to being an ally to various oppressed groups. (I stress in part -- I also blame a generalized mood of personal-life grumpiness, with respect to which I've failed to suck it up and get over it.) I've read a variety of "how to be an ally" type articles over the years, mostly written by members of the allied-with groups. They tend to highlight two major failings characteristic of newly-minted allies* -- attempting to take over the allied-with group's spaces or movement (using your privilege within, rather than against, that group), and walking on eggshells due to a sort of impotent paranoia about making a mistake. It makes sense that these two failings would be salient to allied-with-group people, since they're the ones that directly affect that group, i.e. the things that drive a wedge between allies and allied-with people.
I would add meanness to the list of pitfalls for those approaching ally-ship. Meanness is directed outward, a sort of scattershot viciousness directed at any example of oppression (however serious or mild) that crosses your path (including, occasionally, things that you mistakenly assume are examples of oppression). The mean proto-ally, overconfident in his or her newfound enlightenment, finds seemingly less-enlightened others and unloads their fury on them.
The opposite of meanness is not necessarily kumbaya-type understanding others' position and respecting it and compromising with it (of the sort many progressives have accused Barack Obama of exhibiting). The problem with meanness is not the hard line it takes toward those you're criticizing. The problem with meanness is that it's narcissistic. Meanness is characterized by a focus on venting your negative feelings toward your target, rather than carefully choosing your approach and words for maximum effect in engaging your target. Like the other forms of ally failings, it stems in part from an illicit attempt to conflate your own position with that of the allied-with group, to try to practice the same kind of righteous anger they're entitled to without the prerequisite wounding that makes righteous anger rhetorically powerful and morally legitimate. And meanness is narcissistic in another way -- it often involves a (conscious or unconscious) desire to show off your enlightenment to the allied-with group, to wave in front of them the heads of dragons you've slain. But members of the allied-with groups are typically fairly consequentialist about allies -- they want to be less oppressed, not just to have cheerleaders agreeing with them about how oppressed they are. And meanness is in a third sense narcissistic, in that it can involve a projection of one's own self-loathing. New allies have to deal with a lot of self-loathing -- justifiedly so, as they have just come to understand how loathsome many of their attitudes and actions are. But productive, transformative processing of self-loathing is difficult. It's much easier to attack those who are a few steps farther back on the path, to loathe them or what they're doing in the hopes that it will purge your own flaws.
So I've been mean. I will strive to be less mean, as it's unhelpful to anyone. A heads-up to Alon Levy: If I don't succeed in chilling a bit, you may have to take back that thing you said long ago about me being the only civil blogger.
*I deliberately vacillate here between describing people as new allies or would-be allies -- because I don't know what qualifies one for the title of "ally," or even if an (alleged) ally has the right to bestow it on him/herself or anyone else.