Politics in the sense of the title isn't limited to identifying with one faction within a party system; it has more to do with entangling your identity with us-vs.-them factionalism more generally. Now, in a two-party system, the battle lines are drawn a lot more clearly than in a multi-party, which provides the conditions for identifying strongly with a literal political party; a Democratic voter in the US probably thinks of their elections in more partisan terms than a Lib Dem voter in the UK, and both are probably more partisan than a UMP voter in France. But politics isn't just party politics, and it's entirely possible -- common, even -- to mind-kill yourself by identifying with ideologies, concepts, or people that don't align closely with the party system in your country.
These can be as large as nations: read the YouTube comments on anything vaguely touching on international politics for an unfortunate object lesson. Or they can be more-or-less conventionally political movements, just not ones that have clear party representation: libertarianism, say, or social justice. Sometimes they're single issues, like immigration limits or environmentalism. Ethnic or linguistic groups; sex and gender; bodily features; religions; you get the picture. Basically anything where you can draw a line with people like us on one side and people not like us (you know, the bad guys) on the other.
Basically anything where you can draw a line with people like us on one side and people not like us (you know, the bad guys) on the other.
The problem is that this is how human societies operate. Sweeping it all under the mind-killing rug essentially leaves people unable to discuss social issues.
One of my favourite Less Wrong articles is Politics is the mindkiller. Part of the reason that political discussion so bad is the poor incentives - if you have little chance to change the outcome, then there is little reason to strive for truth or accuracy - but a large part of the reason is our pre-political attitudes and dispositions. I don't mean to suggest that there is a neat divide; clearly, there is a reflexive relation between the incentives within political discussion and our view of the appropriate purpose and scope of politics. Nevertheless, I think it's a useful distinction to make, and so I applaud the fact that Eliezer doesn't start his essays on the subject by talking about incentives, feedback or rational irrationality - instead he starts with the fact that our approach to politics is instinctively tribal.
This brings me to Joseph Bottum's excellent recent article in The American, The Post-Protestant Ethic and Spirit of America. This charts what he sees as the tribal changes within America that have shaped current attitudes to politics. I think it's best seen in conjunction with Arnold Kling's excellent The Three Languages of Politics; while Kling talks about the political language and rhetoric of modern American political groupings, Bottum's essay is more about the social changes that have led to these kinds of language and rhetoric.
Video of a related lecture can also be found here.