Without a scientific study it is hard to apportion greater rudeness to out of staters.
Thus we are left with our own observations.
I think that people who have a hellish commute to work drive more aggressively than others.
There are plenty of rude drivers to be found.
When it's a green plate, one might mutter "rude" under one's breath.
When it's a red and white plate, the same rude conduct receives an extra label that begins with "Mass".
While many might say that there are far more red plate events, it could be that they are just better remembered.
Perhaps I can get some Covid money to study this.