I think some behaviors which may be considered arrogant can be justified. For example, dismissing other people's opinions out of hand can be a good choice when actually surrounded by people with very low-quality opinions.
As for appearing arrogant to others - it may be a difficult-to-avoid side effect, or it may have value of its own - there are social contexts where acting arrogant is useful.
Is it arrogant for HPJEV to consider himself to know better than the adults around him? Maybe so, but he's right about a lot of these things. (I believe there's a significant subset of HPMOR would-be readers who found Harry insufferably arrogant. Does that mean he should change his behavior?)
Having tabooed "arrogance", one of the interpretations is "emotional attachment to the idea of one being right". That, I think is a real problem for an aspiring rationalist - you need to be able to consider the possibility of being wrong.
As DanielLC says, you should calibrate yourself and neither strive to underestimate nor overestimate your abilities.
I want to be able to assure myself that this or that intolerable academic will be magically punished with a decreased capacity to do good work
(If they aren't well-calibrated, that seems like a likely outcome.) Edit: not sure about this part.
Quote: I think some behaviors which may be considered arrogant can be justified. For example, dismissing other people's opinions out of hand can be a good choice when actually surrounded by people with very low-quality opinions.
This is to appear arrogant yes. This is stupid because you can dismiss ideas without being a dick.
To BE arrogant, to believe yourself superior, is bad for a rationalist, because it will hurt more if you are wrong and hence you will have a harder time cooping with new evidence.
Which is basically what you said in the end, you need to...
I have this belief that humility is a part of good critical thinking, and that egoism undermines it. I imagine arrogance as a kind of mind-death. But I have no evidence, and no good mechanism by which it might be true. In fact, I know the belief is suspect because I know that I want it to be true — I want to be able to assure myself that this or that intolerable academic will be magically punished with a decreased capacity to do good work. The truth could be the opposite: maybe hubris breeds confidence, and confidence results? After all, some of the most important thinkers in history were insufferable.
Is any link, positive or negative, between arrogance and reasoning too tenuous to be worth entertaining? Is humility a pretty word or a valuable habit? I don't know what I think yet. Do you?