I'm pretty sure that artists are pissed because techbros have taken the artists' creations without permission and used them to train computers to mimic the artists. This is bad for a host of reasons. One obvious reason is that the thieves can then use this to make money, using the artists' work but without paying them - ever. Another reason is that since the AI can make work using the 'style' of an artist but without the creative direction of the artist, it devalues the style that the artist has worked to create. The new AI created work looks similar, but is not of consistent quality. Another reason is people generally think of art as a creative outlet; where someone's thoughts and efforts go into creating something. But if the work is done effortlessly, and primarily through the lens of what the AI sees rather than what a person sees - then it just devalues art and artistic creation itself. Art creation is basically the very worst thing to automate; economically, morally, and philosophically.