Re: I remember this story.
You're kidding, right? It makes Artoo the most malevolent bastard in the entire sequence of movies, making Palpatine look like a positive noob.
It means that he knows that Darth Vader was Anakin Skywalker, that Luke is Anakin's son and Leia is his daughter, and he doesn't think to tell anyone who might find this information, I dunno, useful?
Does he try to talk to Vader (IIRC Anakin seems to comprehend R2-speak unaided in the Clone Wars cartoon so it should be possible)
Perhaps it's been R2 behind Palpatine all this time, playing a vast, decades long powergame with all the little squelchy organic beings, just for his own amusement. Now THAT might actually work as a story! :)