Daily Battles

So I expect complete selfishness and disregard for anyone else's feelings from the little personalities I work with. I cannot, however, believe that there are some grown-ups that live their life with this very thinking. (okay, I can because I sometimes see it from one very specific person every day) How does one deal with a person like this on a regular basis, especially when it is you who is being victimized? Is there really any statement or comment that can be made to a person like this that will ever change their thinking? The sad thing is that this person has reproduced and is probably molding these little spawns to act eactly the same way: nature vs. nurture... with nurture beating nature.