Looking for Some Intelligent Opinions

I want to describe something I see that is very troubling. Please consider this and respond by telling me why what I see is wrong. I really do want to be corrected.

The political left celebrates diversity seemingly at every opportunity. There is an almost constant battle cry regarding race, national origin, gender and gayness, language, etc., that diversity is a great and wonderful thing.

I fully agree, and can provide any number of accounts from my own life demonstrating the ways in which such diversities are essential to the health of individuals -- myself included -- and cultures -- the United States included.

Here's the disturbing thing I see, leading to the question I am asking: It seems that all this celebration of diversity seems to die away abruptly and with a vengeance when the time comes to celebrate a diversity of opinion about controversial issues.

I was once involved in a conversation which included a young woman. When someone quoted Rush Limbaugh, this woman called him a "fat fascist." Why did this young woman, who was quite vocal in her beliefs about tolerance, suddenly become so intolerant? Further discussion revealed the source of her intensity. Rush Limbaugh, she explained, is "intolerant," and wants to enforce the "systems of oppression" that keep "disadvantaged groups" from "justice, equality, and full participation in society.

Fair enough. Let's all agree that Rush Limbaugh is actively promoting such an agenda. In fact, lets add to the foul odor of it by adding pompous windbag, Right Wing extremist, White House talking points, war monger, bigot, homophobe, and greedy capitalist capitalizing on an uneducated listening audience that unquestioningly marches to his orders. (Rush Limbaugh is certainly not the point here. He just seems to be an easy example to explore the question.)

OK, are we all on the same page? Good. Then here's my question: Why is diversity wonderful with regard to race, national origin, gender and gayness, as I am certain it is, but undesirable with regard to the expression of differing viewpoints? More to the point, does someone deserve the self-satisfaction of feeling like a tolerant person if that person is intolerant of whole groups of people, namely those who disagree with her on many points that she holds dear?

Most importantly, is all that celebration of various kinds of diversity creating a powerful, political monolith that wants to stamp out diversity in one particular context -- the arena of ideas? What if a woman, gay person, member of a racial minority, or undocumented worker begins to proclaim opinions that agree with Rush Limbaugh? Will all the other kinds of diversity still be celebrated with reference to that person?

The most important literary source of contemporary Liberalism is arguably John Stuart Mill's On Liberty. Mill's book turns the whole state of affairs I have described above on it's head. He seems to believe that diversity of opinion on all matters of discussion is the matter of first importance if a society is to be just and civilized. And he offers some pretty good reasons, I think.

Please tell me what you think.