Tribalism makes us stupid. Long term is is a survival mechanism that has made us the dominant species on the planet. By design we minimize any 'bad' acts from 'our team', while horribilizing any acts from the other team. It's like in the Simpson's when Millhouse sinisterly tells everyone the Shelbyville kids love candy 'for the sweet sweet taste' (don't we all?).
I am guilty of this all the time. I see a Florida plate and start looking for how bad a driver they are. I see an Air Force sticker and start looking for inconsiderate behavior. You pulled up in a Porsche, do I need more evidence you're a snob? Have a Marine Corps sticker on the back - I'm sure you're just running late and didn't mean to cut me off. Driving an old car - I get you don't have AC I would speed too etc.
Of course, all tribes have jerks, all tribes have angels. Most folks don't mean you any ill, they aren't really thinking of you at all.