Copyright infringement does generally require you to have been aware of the work you were copying. So for sure there's an issue with using AI to generate art where you could use the tool to generate you an image, which you think looks original, because you are unaware of a similar original work, so you could not be guilty of copyright infringement - but if the AI model was trained on a dataset that includes an original copyrighted work that is similar, obviously it seems like someone has infringed something there.
But that's not what we're talking about in the case of mickey mouse imagery, is it? You're not asking for images of 'utterly original uncopyrighted untrademarked cartoon mouse with big ears' and then unknowingly publishing a mouse picture that the evil AI copied from Disney without your knowledge.
I think this is exactly the problem that many artists have with imagine generators. Yes, we could all easily identify if a generated artwork contained popular Disney characters - but that's because it's Disney, owners of some of the most well-known IP in the world. The same isn't true for small artists: There is a real risk that a model reproduces parts of a lesser known copyrighted work and the user doesn't realise it.
I think this is what artists are protesting: Their works have been used as training data and will now be parts of countless generated images, all with no permission and no compensation.
So Disney don’t need to worry about AI art tools - so ‘attacking’ them with such tools does nothing.