Don Cheadle -- Screw Card Counting -- Casinos are the Villains

Don Cheadle doesn't know jack about card-counting, but he's definitely on Ben Affleck's side ... because he clearly thinks the casinos are the real bad guys

Our photog got Don leaving Locanda Portifino Friday in Santa Monica ... and the Oscar winner was on him game. He knew it wasn't illegal to count cards, and he doesn't feel the least bit sorry for casinos which he thinks cross the ethical line all the time.

TMZ broke the story ... Ben was booted from the Hard Rock for allegedly counting cards at the blackjack table.