Let's unpack this one for a second.
First, the idea of dark patterns in UI/UX is a relatively new concept, so the ethics are naturally going to get muddy. So pretending to be handy wavy about "just be ethical" is not fair to UX/UI people.
Let's take an example dark pattern of "are you sure you want to cancel" taking 3 modals to complete. Each modal tells you something about the app that you may not have. The UX'r does an A/B test and finds that only 23% finish cancelling after implementation of the 3-step modal. So to one user this is a nuisance having jump through 3 modals, but to another user they learned on modal #2 about a product feature they didn't know was possible and decided not to cancel.
Is the UX'r morally wrong for putting in the 3-modal even though in one case it was a nuisance and in another it was beneficial?