I've found quite a lot in my career that often people mistake understanding someone elses line of thought as acceptance of such a thought. This invariantly upsets someone that to be quite frankly isn't mentally equipped (and no I not using that a euphemism for stupid, I mean they literally cannot have conversations about ideas and that maybe due to a number of reasons that have nothing to do with their intelligence) will become upset and then you end up in an argument and the conversation is derailed.
Also simply examining pre-conceptions of why a problem exists also seems to upset some. Normally because you are undermining their authority in one manner or another or they have accepted the initial pre-conception cannot be incorrect because it is normally considered to be inevitable.