^The EMH was created to be an emergency medical supplement, not a fully aware member of the crew. He was only programmed with medical knowledge, not a complete Starfleet database. Anything he learned beyond that was through his own efforts. And why would he have bothered to brush up on the political situation back home?
When the doctor became sentient, he was an intellectual man, I find it rather unlikely he wouldn't keep up with the news from back home.