I love The Verdict, but it's mostly my love for Paul Newman that guides my affection. I'm not sure why anyone should be ashamed of the ending, but maybe I'm not remembering something.
I felt the characters were drawn so broadly that the whole thing was laughable. The insanely corrupt judge blatantly siding against Newman, the transparently evil, all but mustache-twirling lead defense lawyer, the poor wholesome nurse who now teaches inner-city children. Like much of the rest of the movie, it all felt completely manipulative to me.
The reason I assume Mamet would retract the ending, though, has more to do with the fact that he has the jury find the doctor guilty despite being instructed by the court to disregard the only incriminating testimony there is. It's a 'brain-dead' fantasy of justice against the fat cats, and ironic given his comments on the Spector case.