If orca associate humans with taking their food, killing whales (eg: Faroe Islands), and polluting their habitat it's not surprising for them to instinctively react against this threat.
Exactly, I don't believe one bit that they're "attracted to the pressure differential of the prop." I've swam in the ocean and boats are extremely noisy and annoying underwater. The Orcas fully understand that the boats are linked to the changes in the ocean.
To the downvote: I'm sure you've heard a drone buzzing above your head and getting nervous. A boat propeller does the same thing.
Granted, this was a lonely little fellow. But, he knew perfectly well what he was doing and repeatedly approached boats, despite the noise. He died after colliding with a tugboat prop.
Orca will kill other whales simply to eat the tongue. The idea they would be offended by Faroese hunting and killing other species of whales... seems unlikely. Competition seems like better motivation.
Monkeys groom one another to remove lice.
Humans are the lice.