Why, the same way you can turn on a dime to defend George Bush: special vocabulary and a tightly defined context created by recognized professionals. ;)

Critics are paid for their opinions. Some critics are famous for panning everything including their mothers' taste in men. Some critics would give five stars to a nursery school fingerpainting display. Some critics enjoy the shocking. Some critics wish we would return to the 19th century. To paraphrase a familiar saying, critics are like streetcars. Stick around: if this isn't the right one for you, another will be along in ten minutes.

The sum total of all critics' work is what produces the body of criticism for a particular piece or a particular artist. Like it or not, critics have the authority of sheer exposure to art every day that gives them credibility as a group. You don't have to agree with their collected or individual opinion, but opinion is not subject to proof the way science is. You can take the famous approach, "I don't know art, but I know what I like", and you will be correct. You can say, "I know art and I don't like that piece/variety of art" and be correct again. You can say, "That's not art" and be wrong. It's art if it's created from the human imagination.

The immediate value a piece of art has to society is measured by the interest it creates among the general public, the emotional resonance it has (disgust might actually be the object of the Barbie artist, in which case, he wins), the pure aesthetic pleasure it produces, the number of other artists it influences, and, something you will appreciate as a free market fan, the amount of money people are willing to plunk down in order to walk out with it.

(I had the unhappy experience of falling in love with a vibrantly beautiful still life yesterday that elicited such feelings of nostalgia for representational masterpieces of the early 1800s that it pained me to walk away from it. But I didn't have $750 to spare. My muffler needs to be replaced.)

Great art will be judged by its effect on contemporary society together with its durability once the society to which it is contemporary goes away.

A great deal of art is produced every day. Only a small amount of it will survive to be included in the lists of the next century. Of that, ever smaller amounts are winnowed down to be included in the lists of the truly seminal. Harold Bloom, in his outstanding overview of Western literature and its founding influences, The Western Canon, has included Pinter on his list. Though Pinter is only recognized there for two of his plays (The Caretaker and The Homecoming), compared to seven for Sophocles and everything by Shakespeare, still, the company is not too shabby. Tom Stoppard, who I admire, only rates one.

I maintain that your sole problem with this choice is that you object to Pinter's politics. I could similarly dismiss the work of Jean Racine, one of the finest playwrights ever to write in French and an acute observer of female psychology, by pointing out that in his personal life he was an abusive misogynist pig. I would be correct in the latter observation, but that has no impact on the artistic quality of his tragedies.

I further maintain that you seek to discredit praise for Pinter's work by saying that critics are stupid. Well, yes, sometimes they are. Ralph Waldo Emerson's most shining moment of critical acuity was not his dismissal of Edgar Allen Poe as "the jingleman", either. Yet, when collective criticism speaks long and well of someone, there may actually be something there to praise.