Notice that our boy Dave doesn't actually explain why he's got a problem with Diane's piece: its just obviously "reprehensible."
Ezra Klein, who I've had issues with before, describes the above phenomenon very well:
That is exactly right. What bothers Rosenberg and TFA is that Diane Ravitch is calling the reformyists out for the policies they advocate and the statements they make. Ravitch is making the obvious point, in contrast to their reforminess, that the brave teachers who died in Newtown were career educators and union members. TFA doesn't want anyone to think about this; thus, Rosenberg gets indignant, because he has no response. She's right, he's wrong, and that pisses him off.
By the way, here's what Diane said that Rosenberg found so very offensive:
Oh, my stars! Ravitch pointed out that union membership isn't evil! And that the casual maligning of public school teachers that takes place every day by politicians like Malloy is what is "truly reprehensible!" And that test scores should be the least concern of those who care about our schools!
Poor, poor, David Rosenberg - he just can't take this level of truth telling! Quick, someone get him the smelling salts!
Mercy! Defending teachers unions is giving me the vapors!