I will play devil's advocate.
What probably happened:
The driver did something to piss off Roid-man. Roid-man got revenge by cutting them off and brake checking them. The driver hit them, which Roid-man viewed as an assault on him AND HIS "FUCKING" WIFE.
Roid-man went full retard because of the "assault" on his wife.
Just another view to somewhat justify his actions.
FTFY
