I think what happens is that developers see this instability all the time, and it slowly drives them to the edge, then one day a particular bug, not very important on its own, causes them to go over. If they aren't careful to realize that it's the huge history of bugs driving the rant, then it will come off looking like much ado about little.
I completely agree that this particular complaint is blown way out of proportion. But I think that's probably where it's ultimately coming from.
I agree (from personal experience and obvservation). The cumulative effect of all the little indignities a developer suffers at the hands of Xcode build up like steam in a pressure cooker, until it has to go somewhere. (A rant on a blog, a mouse hurled against a wall, chairs kicked over, whatever...)
I completely agree that this particular complaint is blown way out of proportion. But I think that's probably where it's ultimately coming from.