The reason why they are brusque is not because 'they have been abused' but because, the tolerance for bullshit is low - because of two things 1) they have seen bullshit bring down otherwise promising projects or ideas, and they don't want that to happen; 2) they percieve that varnishing your emotions or opinions with too much tact increases the cognitive load required by the recipient to 'get to the truth'.
Whether or not being brusque or diplomatic actually is effective is debatable. Nonetheless, I think missing this very important concept is generally bad.
In some fields, like science, having to deal with people who will trash your idea with honest commentary - that makes you think twice about what you are doing - is far, far, far better than having to deal with the silent judgement of a failed experiment that lets you down dispassionately, and wondering, "why didn't anyone care enough to tell me I was stupid to try this".