Well, if you believe that games are art/expression, then they should represent varying facets of human experience. In other words, sure. I can't say that'd I'd play that game, but I wouldn't sneer if one were made. A high-profile activist game would surely stir things up and make for some interest discussions.

As far as your second question, no, I can't say that I do know of any. Well, aside from the "protect planet earth" trope, but that seems fairly inoffensive.

Generally this, but that's because I would probably end up disagreeing with the "message" (if there's a story), or the "message" would probably not take into account the complexities of the real world. Spec Ops: The Line seems to mean well with an "anti-hero" message, but it has been taken by people to be highly anti-military, anti-America, and some seem to have been relishing in that. (I think it was Zero Punctuation's video that kinda rubbed me the wrong way on it.)

On the other hand, I have fantasized about making a game where the main character (a superhero) frees people from tyranny in parts of Africa. He has the ability to knock out soldiers against him rather than killing them. (So basically Superman ... but in Africa.)