Really don’t think it has anything to do with you owning a BMW; instead, I think drivers, generally, have less patience and are more inclined to take offense and respond aggressively.
I say this because there are countless reports of road rage on the news, each involving a variety of cars (Subaru, Nissan, Jeep, etc.). Not saying that a jealous SOB won’t act a certain way towards you out of spite; however, most likely, they’re reacting to you, and not the car you’re driving.
Be safe out there.
