"The AAA Foundation for Traffic Safety found that between 1990 and 1996 road rage contributed to 218 deaths and 12,610 injuries. The study analyzed 10,037 police reports and newspaper stories about traffic accidents that led to violence. What's more, AAA found that road rage incidents increased nearly 7 percent each year within that six-year period."
Not sure what you're trying to say, exactly. "There is proof that road rage exists"? OP didn't say "Road rage doesn't exist", he said "It's not universal". A universal quantifier ("all" or "none") can be disproven with a counter-example (op to article), an existential quantifier ("some" or "not all") can't (you, if I understand it correctly, to op).
in http://www.apa.org/monitor/jun05/anger.aspx