It might be that my current opinion is skewed by the present political situation in my country (Italy). I haven't enough knowlegde of foreign internal politics to judge if the italian situation is typical or not, brief conversations with foreign people on the subject suggest it's worse than in the average developed countries, but not that much. To the point.
There's one main problem of talking about politics: that it doesn't work like it should work, and there's little way to collect enough information to produce a good model of the reality. In practice: politicians, on average, don't try to do what they think to be the best interest of the country. They try to mantain the power and possibly to gain more advantages* from it. They have to pay debts to whoever supported them: the voters base, the powerful industrial groups, the trade unions, the banks and very likely the mafia. Sometimes these webs of interests are in plain sight, but very often they're not. Discussing of politics is therefore very often frustrating at best, since you have to work with partial (and very often wrong) info.
*E.G. the last year the government didn't fell mostly because more than 50% of the congressmen wanted to reach the pension threshold, and therefore need to sit in the parliament for another six months ( Link - in Italian unfortunately )
Certainly skewed by looking at Italy, but most of what you're talking about would be familiar to cynics anywhere.
But "politics is the mind-killer" is more about the tribal affiliation aspects of associating oneself with a party.
Summary: I propose we somewhat relax our stance on political speech on Less Wrong.
Related: The mind-killer, Mind-killer
A recent series of posts by a well-meaning troll (example) has caused me to re-examine our "no-politics" norm. I believe there has been some unintentional creep from the original intent of Politics is the Mind-Killer. In that article, Eliezer is arguing that discussions here (actually on Overcoming Bias) should not use examples from politics in discussions that are not about politics, since they distract from the lesson. Note the final paragraph:
So, the original intent was not to ban political speech altogether, but to encourage us to come up with less-charged examples where possible. If the subject you're really talking about is politics, and it relates directly to rationality, then you should be able to post about it without getting downvotes strictly because "politics is the mind-killer".
It could be that this drift is less of a community norm than I perceive, and there are just a few folks (myself included) that have taken the original message too far. If so, consider this a message just to those folks such as myself.
Of course, politics would still be off-topic in the comment threads of most posts. There should probably be a special open thread (or another forum) to which drive-by political activists can be directed, instead of simply saying "We don't talk about politics here".
David_Gerard makes a similar point here (though FWIW, I came up with this title independently).