I think I get the point, Greg.

It's a variation of the "Everyone knows Elvis is dead, and anyone who says he is still alive is a raving nut-case" argument, isn't it?

The refined version becomes:

"Everyone knows Bill wrote all those plays and sonnets.   Anyone who says otherwise must by a raving nut-case."

Got it.

Against such powerful and overwhelming rhetoric, I am forced to concede defeat.    Ah well, such is life.   It must have been Bill after all.