They don't. A homely analogy: I grew up in a town with a very large Latino population. So whenever I hear some statement about "the Mexicans," I listen about possible group traits but I also know my friends Chris, Hank, Yolanda, etc in their individuality. I also grew up with many gay friends --but wasn't aware until years later that I had done so. It was only from college age onward that I had lots of friends who were out as gays, which inevitably affected my view of "the gays" and made me wince in recalling the standard thoughtlessly cruel high school jokes about "the fags." One reason opposition to same-sex marriage is sure to disappear is that straight Americans born after about 1980 have always been aware of having gay friends and can barely fathom the "threat" posed by their right to marry. (For proof, see here.)
Of course, close contact between different groups doesn't always build amity. (See: history of Northern Ireland, West Side Story, etc.) But the real secret of American inclusion through the generations is that when you grow up with, work with, live next to, intermarry with, and in all other ways get to know people from different categories, you have less patience for generalizations about "the blacks" or "the Irish" or "the Jews" or "the gays" or "trailer trash" etc.
By chance, like the (Hindu) reader I quoted yesterday, I've had a lot of Muslim friends over the years. They're from outside the country, thanks to our years of living in (Muslim-majority) Malaysia, where our house was near a mosque, and visits to my wife's parents when they lived in (overwhelmingly Muslim) Indonesia. They're from inside the country -- mainly immigrants or children of immigrants from Iran, Iraq, Turkey, Bosnia, Saudi Arabia, Xinjiang/China, and elsewhere. They have as much in common with Osama bin Laden as I do. So when I hear that "Muslims worship violence" or "Muslim life is cheap," I think this is either ignorance or bigotry, and it's claptrap in either case.
This brings us to the second category of response: that the person in question, Martin Peretz of the New Republic, is actually a great guy in other ways. In consummate quadruple-backflip contrarian style, Jack Shafer makes that case in Slate (while also noting Peretz's "irrational hatred of all things Arab -- and by extension Muslim"). In a more heartfelt way, even suggesting that we are seeing a "war on Marty," so do my colleagues Andrew Sullivan and Jeffrey Goldberg.
Fine! Andrew has worked with him, as I never have, and both he and Jeff Goldberg know him in the round, as I do not. They can put bigoted comments in perspective, hating the sin (I hope!) but loving the sinner.
But this really is the point: Because they know him, they extend an "in the round" view to him -- the very view that this "Muslim life is cheap" would deny to a billion of the world's people, including many millions of Americans. We all deserve to be seen in the round. Even "the Muslims."