
Well, I used to get mad, and either try to communicate my anger to jerks,
or to, uhm, educate them in how to improve their manners in traffic.
Now I just try to get them off my tail.

In heavy traffic I slow down a bit, mostly so I have more buffer zone in
front to balance the minimal buffer behind, but I also often find that the 
jerk behind will notice traffic moving faster in other lanes, switch
into one of them, and pass me - which is fine, because then I can keep a
better eye on the jerk from behind, while looking ahead, rather than
from in front, while splitting my attention between ahead and the mirrors.

In traffic so heavy that there is no way for the jerk to pass,
I might pull over, as if to look for a street number or name,
(still ignoring the jerk) just to get the jerk off my tail.  

If this all sounds, well, wimpy or un-Denizenly or pessimistic, or perhaps 
(for any psych types) passive-aggressive, consider that I prefer to get
my adrenaline jollies from riding, rather than from yelling at jerks.  

A ride can improve my whole day, while yelling at a jerk is likely (for
me) to ruin my ride or my day with my own anger.  In the worst case,
yelling at the jerk could ruin my life - since even a tiny jerk in a
cage behind me is better armed (with the cage) than I am on a bike. 

On the other hand, you might try subtly arranging to be the last
vehicle to legally cross one or more intersections, leaving the jerk
waiting for cross traffic (and thus off your tail), or crossing
illegally (hopefully in front of the waiting police).

Like almost everything here, your choices and mileage will vary.
