NEW YORK — Norm Madonald fired back at Don Ohlmeyer just one day after NBC confirmed to Daily Variety that its West Coast president had banned MGM ads for Macdonald’s new movie “Dirty Work” because of the exec’s continuing feud with the former “Saturday Night Live” star.

On “Late Show With David Letterman,” which taped Tuesday afternoon for broadcast last night, the host, himself an emigre from NBC who is no fan of Ohlmeyer’s, launched right into the controversial topic.

“Now, Norm, let’s just do the math on this,” said Letterman. “NBC is owned by General Electric, maybe the single biggest global corporate entity on the globe. And they’re generating several billion dollars a year. What the hell could they possibly care about you and your movie?”

“I don’t understand it at all,” said Macdonald. “First of all, he’s best friends with O.J. Simpson. And that’s fine … Now, how could he not like me?”

Letterman, after surmising that Ohlmeyer “doesn’t have to kiss up to Seinfeld now, so that’s freed up his whole day,” said Ohlmeyer’s move amounted to “terrorism. This is completely uncalled for. “They’re afraid because they fired you, that you’re going to come back and bite them in the ass. That’s what they’re worried about.”

Indeed. Macdonald explained that “in this movie I actually get revenge against this rich jackass who makes my life a living hell.”

“Well, there you go,” replied Letterman.