Fair use is relevant for parodies that are not subject to copyright or royalties so it is indeed relevant, but you're right, the issue with Bette Midler is the

Fair use is relevant for parodies that are not subject to copyright or royalties so it is indeed relevant, but you're right, the issue with Bette Midler is the common law right of publicity, of which David Guetta is not in the wrong because no one was tricked into thinking that he was Eminem. Even if David Guetta's DJ sets became nothing but Eminem songs it would be fine because he would still not be tricking anyone into thinking that he was Eminem.