Why? Because he is cooperating formally and materially with the mortal sin of murder. By installing the plumbing for the Two Rivers Planned Parenthood Abortion Mill in northeast DC, he is no different than those who constructed the Nazi death camps of 85 years ago. Moreover, he's quite cavalier and callous about the matter. He admits he's doing it only for the money and that he would do so for the Ku Klux Klan. Well, I suppose he's at least honest and consistent regarding his moral depravity. But would you want him in your home doing your plumbing?
Here's the DC permit with his contact information so that you can make an informed decision. Below that is the video in which he struts his immorality.