They are called gentle giants because they look gentle when swimming. If you go near the tail or fins, you could literally be knocked unconscious with internal bleeding or even instant death.
What im trying to basically say is that, a whale would never let you get close without attempting to hit you with a tail or fin. Of course there are certain cases like above where it trusts humans enough to let itself be touched.
"That's because I spit on it, you didn't?"