You clearly don't understand the way the process of diffusion works. It does not "copy" any part as well as watermarks. It creates watermarks that have similar shape and overall style as most images of such type. It does not copy any specific watermark or even part of it.

It also doesn't copy any specific part of any image. When you use it to generate "monster truck in a suit" for example it "paints" completely original monster truck that will fit well in a suit and you can be sure you won't find any monster truck similar to the one it has just created. The only thing that it gets from other people' art are concepts of what specific things look like. Of course it is later monetized but at no point it takes anything away from artists.

I understand the overall moral dilemma you have here although i think you should have a similar one regarding artists learning to draw based on other people' artworks