I don't think it is unfair - Michaels's position on racism and sexism really is superficial. While he has a good argument against the language of "diversity," he accepts the premise of liberal multiculturalism, that diversity is the correct way to understand issues of race and gender; hence why he thinks class is different from, and more important than, race and gender. It doesn't occur to him that it might be possible to think about race and gender as systems of oppression that are as real as class (although Michaels doesn't actually have a theory of class, either; he has a much more liberal theory of "inequality").
What he ought to do is apply the critique of diversity-focused understandings of class that he puts forward in that LRB piece, to diversity-focused understandings of race and gender. I find it difficult to believe that, as a professor in an English department, he is unaware of the possibility of doing so. It's an extraordinary political and academic dereliction of duty that he doesn't reference any of the relevant material from, for instance, feminists of color, marxist-feminists, or critical race theorists, in "The Trouble With Diversity," and it suggests that he isn't serious in his purported support for anti-racism and anti-sexism.
--
"The slightly richer ... eat in semi-darkness, preferring
candles to electricity. These candles make me laugh. All the
electricity belongs to the bourgeoisie, yet they eat by
candle-end. They have an unconscious fear of their own
electricity. They are embarrassed, like the sorcerer who has
called up spirits he is unable to control."
-- Vladimir Mayakovsky http://blog.voyou.org/ voyou at voyou.org