I am curious, what is he telling potential employers about why he was let go? Is he up-front about being fired because of A? Or does he say something like, "There was a restructuring, and people at all levels were let go." These days, most employers offer a terse reference check, verifying dates and title only, so a little stretching of the truth is an option.
See, I was fired because of an affair - my wife's. I got so depressed, distracted, demented, etc. because of the affair that I lost focus at work, and they let me go.... in a "restructuring," if you know what I mean (wink, wink).