It happens, I hate it, ignorant self centered people really tend to bother me but, I have had to come to grips with it as the stress from thinking about it was starting to affect my health. It is like 3oaks said in his post about the me,me,me generations. Now when I am coming up on an on ramp I work over to the next left lane and leave the right lane open for the goofy person that could be coming on and protect my family and let it go.
It's not going to get better folks, it is going to get worse. Practice defensive driving, know the law but, it's not worth getting into a crash just to be right as far as my driving is concerned.