I was that guy.
Harp relentlessly on the prequels, and how Lucas utterly betrayed everything remotely good about the original three. Make sure to stick in the fact that the Thrawn books were ruined by canon before the other ones (except Splinter of the Mind's Eye, but that's what you get writing fan fiction between movies like that). Bring up the shitty stuff from the special editions. DO NOT let him weasel out of feeling bad. Lucas did BAD THINGS and if we don't talk about it other people will keep doing those bad things.
The only appropriate entry points for this guy will be the occasional episode of TNG or the JJ Abrams movies. TNG because I assume he's around our age and LeVar Burton, and the new movies because they're less Space Communists and more Bad Boys In Space.
You should both watch some Firefly if the process is too contentious. Every nerd loves Firefly.