Carlos feels guilty for even trying to make a joke out of it because now Jane knows that much more horrible-ness exists in the world and he'd honestly rather shield her from it. But part of him can't help but want to be honest with her because he needs her. It's selfish.

"You don't need to say that..." Carlos murmured, because it's not like it's her fault or there's anything that anyone could honestly do. Even if the Isle hadn't been so horrible his mother would have still been Cruella.