To put in shortly, Wilbur hates Eret because they betrayed him by telling Dream where him, Techno and Phil are (Phil and Wilbur are Wild witches, which are illegal, and Techno has basically made himself illegal for attacking a guard and simply because he's a human, which just... don't exist on the boiling isles). the 3 almost got arrested because of that! and now Wilbur's really pissy at them and will have a hissy fit whenever seeing a poster on the Healing Coven