Well, Zero himself is testing much things out and he even posted fanart about his work in his art folder, so I guess he really don ´t mind it at all if ppl use AI to make fanbased pictures of his stories and art. So the "stolen art" saying is maybe a bis too harsh, as long as ppl don ´t copy his art to make profit out of it.
AI itself will being a part of the future, it can ´t be helped, there might be a time where you can ´t see if something is AI made or hand drawn, as long as the quality is ok of AI works I don ´t mind it.
The positive thing is, we will see more art in the future, the negative thing is, it will lose some of it ´s charme, I think it´s the same like in movies for example, hand drawn cartoons just look better then the computer animated stuff, at least for my taste. But there are some well done computer animated movies too, so maybe it ´s more a thing about the content/story itself and not primary of the way the art is done, time will tell.