I'd say nationalism is less worrisome for LWers than X-ism, where X is some tribe that inspires tribal thinking but that isn't usually seen as a tribe.

I'm not! Yay us, boo them!

I don't think I've ever seen a bunch of people quite so full of habitual self-doubt as the folks on Less Wrong. Personally, I just don't see how nationalist fervors even work. Rallies of any kind have always left me cold, even when everybody around me is cheering their lungs out. There's no way I could start thinking thoughts like "My country, right or wrong" for more than three seconds without stopping to root out the infection -- a familiar feeling by now, actually, since knowing about cognitive hazards often makes it possible to recognize when you're slipping into one. I don't think I'm unusual among LW-denizens in this respect.

But by all means, keep on being uneasy about this. That's probably prudent.

For myself, I am painfully aware of my vulnerability to nationalism. I blame it on the years of propaganda from the entire cultural context I grew up in.