Why would a Nationals fan root for Cody Ross? He was definitely a Nationals killer.
Because he's a great player, who got claimed off waivers in the middle of the season, and has gone on to wild success? As long as he's not playing the Nationals, that doesn't factor in remotely. As bad as this team has been, who hasn't been a Nationals killer? If I started rooting against anyone thats had success against us, not only would I end up rooting for no other teams in baseball, I'd also be rooting against half the players on the Nationals at some point.