I often encounter (especially among academics) people who are quick to refute questions or ideas on trivial grounds based on trivial formal description errors of the type described in this post. To any non-expert the intent of the ideas or questions is clear, but the formal thinkers are often quick to dismiss based on these trivial inconsistencies. I have a strong aversion to being dismissive or mean to people, especially in public, so by default I reinterpret in those cases - "If by X you really mean Y (where the difference between X and Y is only clear to an expert well-versed in formal descriptions of the subject matter) then yes, that is an interesting idea - the pros and cons are as such...". 99% of the time they actually mean Y, but they're just not quite well-versed enough to phrase it that way - or, upon knowing that swapping from X->Y converts their statement from trivial to meaningful, they would often be happy with Y capturing the sentiment they wish to convey.
I have started proselytizing this approach to my colleagues, because some of them are simply too formally minded to "pull themselves out" enough to interpret such statements generously. I do think some subset do use this sort of denigrating approach to cement their authority, which I find silly.
This is interesting because I work with professional mathematicians and they are the exact opposite. They always start off with a semi-formalized idea and play with it a lot before trying to hone in on something formal. And conversely they have absolutely no problem listening to / thinking about non-rigorous ideas. They also do excellent work, so I would say this is a positive trait wrt productivity.
I don't think there's much better advice than what the OP has already said: train yourself to wonder if there's a deeper question that the asker might be asking. Ultimately it's a question of humility. I think dismissiveness is often motivated by an assumption that the asker has made a simple rookie thinking error, and that an involved answer isn't worth your time.
I too fill in the blanks and expect the same courtesy to be given me. As such I have began to bluntly refuse to participate in discussion with an uncooperative party like what you describe. I can find more constructive things to do with my time and they have no reason to expect otherwise.
Like you say, it's very curious why some people do expect their attitude to be accepted. If it is something they have learned to do, then what can be done to make them unlearn it? My attempts at this have so far clearly been too blunt, probably since I'm no saint and seldom suppress my irritation at their intellectual dishonesty faster than thinking of a scathing way to confront them...
I expect there's a fine line here between being generous and being seen as patronizing, but I try to cultivate a similar mindset (with varying degrees of success). I've always found it a sign of someone trustworthy, generally possessed by much more experienced colleagues.
I have started proselytizing this approach to my colleagues, because some of them are simply too formally minded to "pull themselves out" enough to interpret such statements generously. I do think some subset do use this sort of denigrating approach to cement their authority, which I find silly.