and I'm sure Ariel's reason for leaving Eric was that she saved Blackbeard (with a good reason, of course) and felt the responsibilty to help stop him from terrorizing people.
And, as far as Gold being a villian without good intentions, my hope is they give us a reason for him being the way he is... Maybe he actually is trying to get Neal written back into the story, or maybe he feels he has actually lost everything, so he might as well go all out. He stil has a grandson he loves(?) so that's confusing.
It's just kind of weird having a character/antihero with so much depth, that you felt like you understood, go to being a villian without cause.