Copying an artist's style isn't in and of itself looked down upon, any artist will tell you that doing so is an important part of figuring out what aspects of it one likes for their own style. The problem with AI copying it is that the way the vast majority of users are using it isn't in artistic expression. The majority of them are simply spamming images out in an attempt to gain a popularity "high" from social media, without regard for any of the features of typical creative pursuits (an enjoyment of the process, an appreciation for other's effort, a desire to express something through their creativity, having some unique intentional and unintentional identifying features).
Honestly maybe the West messed up having such broad fair use protections since it seems people really have no respect for any creative effort, judging by all the AI art spam and all the shortsighted people acting smug about it despite the questions around it being pretty important to have a serious conversation about, especially for pro-AI folk.
The AI art issue has several difficult problems that we are seemingly too immature to deal with, it makes it clear how screwed we'd be as a society if anything approaching true AGI happened to be stumbled upon anytime soon.
That is based on the fallacy that derivative creativity is somehow lesser than so-called “original” creativity.
The vast majority of AI art I've seen on sites like Pixiv has been 'generic' to the level of the 'artist' being completely indistinguishable from any other AI-using 'artist'. There has been very little of the sort where the AI seemed to truly just be a tool and there was enough uniqueness to the result that it was easy to guess who the creator was. The former is definitely less creative than the latter.