The best way I can describe it is this. Most guys that are drag racing assume that the car is only going straight. That's great if that's what happens, but eventually the car will get out of shape.
Anyway, guys take the average street car and turn into a drag car. The first thing they do is take off the front sway bar. Now lets assume the guy follows the same old recipe of 90/10s, lower spring rate, etc... The front is now loose, and the front wheels can move independently from each other. The car will act like an old 3 wheel ATV in a hard turn if it has a stiff rear bar in it... They outlawed 3 wheel ATVs.
I am not suggesting that the above is the proper way to set up a car, but it is way to common. If you have a stock(ish) front suspension (this car) and are considering a rear bar, MY advice is to have a front bar.