Recently I came upon a question that said "I want a abstract on...", with no other details. This strikes me as demanding and unreasonable. Should such questions be flagged as "rude or abusive", or am I being over-sensitive to this type of language?
I wouldn't flag it as rude or abusive. I'd downvote it, and possibly explain why the question might be considered unreasonable.
My go-to response to one-liners that ask for volumes of work, is
Try to spend as much effort writing the question, as you'd hope someone would spend writing an answer.
Because what I really don't like is a question that was written (or copy/pasted) in seconds, expecting a hundred times more effort from someone else.
My take is even more tolerant than that: My inclination is to cut people a lot of slack on stuff like this (especially considering that there are undoubtedly a lot of non-native English speakers on this site). This person may have taken a sentence that was entirely polite (not at all "demanding") in their own language and clumsily translated it word-for-word into English. It may be very brief for the same reason (limited English skills). If the meaning of a post is clear, and not overtly rude (like "your answer is stupid", etc.), I think it's totally fine and not the kind of thing SE should be "policing".