Wageslave,
I think that your analogy to the German Wings accident is not really valid in this debate because the weight of evidence, albeit circumstantial, is that in this accident the pilot deliberately flew the aircraft into the ground. This means that the accident was not due to 'pilot error' but was due to an intentional act that was possibly pre-meditated.
I find your comment "Let's show a bit of humility and be a bit more open minded" rather ironic when set in the context of your post. It is those who say 'It is pilot error - full stop' that are the ones who are arrogant and narrow minded not, as you imply, those who await further evidence before coming to a conclusion.
I fully endorse CM's comments in reply to your post. Pilot error occurs, but whoever the pilot was who made the error in question had no intention of causing the outcome resulting from the error. Any error, inevitably, has multiple causes of varying magnitude of influence. We may be able to identify those causes and, through education, training, review of procedures and regulation, reduce the probability of it happening again. Or we may never discover why the error was made, but almost certainly there will have been one or more reasons. In such circumstances an agnostic philosophy is, in my opinion, the best response.