I had someone try and pull a similar stunt on me today. Was on the interstate and had a truck passing me on the left. Apparently the car behind him wasn't happy with how fast he was passing and he tried to merge back over into my lane before he was around me -- forcing me to hit the brakes and shift right to the rumble strip. I honked and gave my single digit salute, to which this person became a traffic weaver with several more close calls as he worked his way down the interstate. The sort of person who you hope winds up in a ditch but doesn't take anyone else with them; but usually just causes a crash and accidents for others and gets away clean.