Yes, selling an exact copy of a copyrighted work is an infringement (giving it away generally isn't). Creating a derivative work, or work in the same style, is fair use.

Generating a digital image of money isn't the same thing as counterfeiting currency.

> I would also not generate pictures of child pornography

Legality aside, why not? Who is harmed?

> There's a reason why SD apply censorship filters to generated images

I'm not sure there is. I don't think any one group of people is uniquely equipped to limit what images another group of people can generate with ML.