What is the purpose of the "per se" added to this sentence?
"per se" - alone, intrinsically, in and of itself.
In law, it is used when to describe actions that are illegal by themselves, eithout necessitating further evidence. For instance, in regard to Blood Alcohol Concentration for drivers:
"A per se statute defines the BAC at which it is presumed that all drivers are intoxicated and cannot drive safely, regardless of actual motor vehicle operation."
So, if your state considers it a crime to drive a vehicle while your BAC is over .08%, you may not argue that you are an experienced race car driver and could demonstrate that you have the ability to operate a vehicle safely despite your blood alcohol level, whereas an inexperienced driver might not be able to do as well while at .07%, or even dead sober. Indeed, even if your driving were perfectly within all legal parameters, the BAC level alone would be enough for conviction.
The law stands on its own, and may be applied irrespective of circumstances. What the civil rights shysters are saying about racial preferences is that, despite the obvious contradiction to the 14th Amendment and the Civil Rights Act of 1964, favoring one group over another is not a per se violation, meaning it is not an automatic violation. Unlike having a BAC over .08% and driving a car, using racial preferences does not automatically create a violation. Other factors may be brought in. What the idiotic ruling by O'Connor and the Four Morons allowed to be brought in was the great need for (the great God) diversity in these situations, which, apparently trumps the Constitution.