"Mickey the Idiot" wasn't military. Eleven may have teased Rory by calling him Rory Pond, but Nine and Twelve repeatedly showed actual contempt for Mickey and Danny in their early meetings. Was it explicitly because they were black? Of course not. Did they treat any other companions' partners the same way? Not that I can think of. Race is what the two companions' partners who were treated like crap by the Doctor had in common. I'm not the first person to pick up on that.
But early Mickey WAS an idiot.