Tolerance: The capacity for or the practice of recognizing and respecting the beliefs or practices of others.

Diversity: The fact or quality of being diverse; difference; A point or respect in which things differ.

For two decades, America’s schools and colleges have made a signal virtue of “tolerance” and the “celebration” of diversity. When skeptics have voiced concerns that these bumper-sticker sentiments pose a threat to free speech and intellectual freedom, or threaten to substitute the habits of therapy for those of disciplined inquiry, they have been dismissed as retrograde curmudgeons. (read the article)

Here's the short scoop: In a food coop at the University of Maryland (where the “human rights code” prohibits discrimination on the basis of political beliefs, along with sex, race, and so on), a worker refused to serve and ring up a client because she was "offended" by the client's t-shirt.

The clerk at this grocery and sandwich shop in the student union read her t-shirt’s “Baltimore Zionist District” and “I Stand for Israel” slogans and then declared, “Your shirt offends me. I won’t ring you up.”

Instead of explaining tolerance and diversity (respecting the rights of others to voice their political opinion), a deal was reached where a worker can refuse service to people they disapprove of, so long as they can get another worker to serve that client.

I do have to wonder what the backlash would be if a Christian refused service to a person wearing a gay pride shirt. (for the record, I'd ring the client up and be very polite and kind doing it)