You're missing the point.
Anybody can criticize anybody else. That's part of democracy. Meanwhile, why the hell are you defending DeLong? He invited the list to dismiss Sweezy, at the time of Sweezy's death, as a Stalinist based on a single line he wrote in 1952. Baran and Sweezy's Monopoly Capital is one of the top ten social science works of the twentieth century.
It's a completely valid and necessary point to reply to DeLong that his point is crap. The fact that Sweezy towers over the DeLongs of the world in intellectual terms merely magnifies the absurdity of what DeLong tried to say.
Nobody here says he has no right to say it. We're merely noting what a huge joke it was to say what he said.