Lets take wealth, for example.
Now, the communists amoung us might pipe up about losing the whole money idea, or at least equilizing wages, ridding ourselves of economic need and thus submersing us all in a family-like bliss. Unfortunately, barring nuclear holocaust or something equally catastrophic, i don't see us accomplishing this kind of society anytime in the next couple centuries, and i'm not so sure it would really solve this problem anyway without returning to the ways of our hunter-gatherer ancestors. So, we're stuck with the wealth classes and there have to be poor people. Ok, lets say we eliminate all mass murders. After a time, that will seem as bad as a mass murder was.