When I ride I'm pretty mellow about other drivers. Alert, certainly, but otherwise indifferent. I know people are going to do dumb things. I know that I'm invisible to 99.53% of the drivers on the road. When I have a near miss I think, "phew!" and not, "you jerk!"
Except when someone's natural stupidity is combined with aggression. When a driver pushes past me mere inches away and then cuts me off, I get angry. When someone in a cage decides that I should share my lane space so they can get to the red light a little faster, I get angry.
In fact, I start to feel a need to accompany these people to where ever it is they're going, and lucidly explain to them how their aggressive tactics come across not only as impatient assholery, but as bullying. Their reckless driving is understood, by me, as a threat. I won't let such a thing stand.
I'm sure they'd understand when I then caved their heads in with a wrench.
No, I'm not actually going to assault the asshats I encounter. It would be a losing battle; there's always another jerk out there swilling a coffee-like-beverage and text-messaging something important like "OmG LoLErZ!" when they should be, ya know, driving.
It sure would be nice to knock the venti half-caf mochaccino out some cell-phone yapping moron's hand and lay some knowledge on them now and then, though.