I think a big difference in how this tech makes people feel is the amount of effort required. It's a problem we see with technology in other areas, too: it's not (much of) a problem if a cop sits outside a suspect's house for a few hours to monitor their behavior. Most people think it would be a problem if the cops pointed a camera at the house 24/7 for months. Pretty much everyone agrees canvassing society with cameras and creating a public space surveillance panopticon is bad. Where's the line?
Similarly, if some artists spend years learning the craft and mimicking a couple of styles with a relatively small output, it's not a huge problem. The scope is small. But if everyone on earth can do it to anyone on earth at massive scale just by typing "in the style of ..." to an AI, does that start to be a problem?