The truth is that born Mainers are just not nice people, especially if they perceive you were born elsewhere, which they call "away." No sense trying to hide it; you are easily spotted by your fully-functioning brain.
Be it from fear of being mocked for their accent, or fear of being mocked for their lack of intelligence, or perhaps fear of being mocked for their poor sense of style, lousy eating habits, lack of sophistication, overwhelming obesity, dumb sense of humor, inbred redneck behavior or incredible cruelty to lobsters, they are simply downright mean.
It's sad, really, because it's quite a pretty place. But the natives...oy.