In this case, it's from a model that is specifically trained to emulate someone's style, SamDoesArts specifically. Any artist would be furious that someone would try to rip off your style and, at best, piggyback off the years of effort that went into developing your style. And thats regarding other artists imitating you, it is so much worse when anyone at all can just rip a bunch of the art you have posted and generate tons of images, bastardising your style, and use for purposes like this where it's not only commercial but also NSFW and tied to a shit tier game.
The "they took our jobs" angle is going to be the one that normal people will sympathise and get upset about the most, and I imagine it is why there's as much outrage amongst the masses. With that said, this abysmal game shows us some other very real reasons why it's not a simple 'good or bad' conclusion when it comes to 'AI' image generation.