Caribou joining is literally the worst One Piece theory ever. Just need to reiterate that. Yes, let the scum with no redeeming qualities join.
The fact is, Robin's evil deeds were only IMPLIED, her name wasn't even known until much later, and it was abundantly clear to anyone with reading comprehension that there was more to her character than what was on the surface from the very moment she appeared.
Caribou is just a sadistic murder. We don't just SEE ACTIONS, we are READING HIS THOUGHTS. There is a huge difference from Nico Robin.
Not even remotely similar. It's about the same as saying Arlong should've joined after learning that he killed Belle-Mere right in front of Nami and Nojiko. "he'll be their fishamn fighter! =D"
Guys, listen Hody Jones is gonna joint his arc and don't whine about my theory. He's not such a bad guy really. That stuff about murdering every human on the planet and dragging their corpses to the ocean bottom…I bet he didn't mean that.