How to tactfully request removal of my name from coauthorship

I wrote a mathematics manuscript (see Extremely mild punishments for academic misconduct), and sent it to a professor, who then attempted to have it published after adding coauthors to the paper. His misconduct is not my concern. My concern is that the manuscript is not of publication quality, and I would prefer that my name not be attached to it. Virtually all of the manuscript is written by me, and all the work was done by me, so I can't claim that it is not my product.

My question is: What excuse do I use to have him take my name off the manuscript?

I would prefer to remain on good terms with this professor. I would also prefer not to mention in any way that the manuscript is worthless, because it solves a problem that he had been attempting unsuccessfully for quite a while, and such a statement would be deeply challenging to his pride.