In brief, I think my interpretation is right because it is consistent with the intended lesson, which is "Don't talk about Politics on LessWrong." In other words, I understood the point of the story to be that treating arguments as soldiers interferes with believing true things.
I agree that "bad ideas should be publicly challenged" is only true if what I'm trying to do is believe true theories and not believe false theories. If I'm trying to change society (i.e. do politics), I shouldn't antagonize my allies. The risk is that I will go from disingenuously defending my allies' wrong claims to sincerely believing my allies' wrong claims, even in the face of the evidence. That's being mindkilled. In short, engaging in the coalition-building necessary to do politics is claimed to cause belief in empirically false things. I.e. "Politics is the Mindkiller."
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).