I've confronted a motorist when extremely angry before, and that was unproductive and dangerous.

I've confronted another when the situation was clearly in my favor when I was calm, and that went really well (the car ended up stuck at a light, the driver and his girlfriend were too sheepish and embarrassed to look me in the eye) but that was a rarity.

I generally don't confront. Too many ways to go seriously wrong. Too few that end up productive.