I've watched They Live with people who didn't really get what it was about, but it made for some interesting discussion afterwards that got the gears in their head turning regarding leftist ideas.

Alternatively, Jaws:

"I read Jaws" said Castro. "It's not a very good book, but I think the movie must be good because it's a Marxist picture."

"Oh?" said Coppola.

"Yes, it shows that businessmen are ready to sell out the safety of the citizens rather than close down against the invasion of sharks."