I think you're right. With other deserving candidates, voters will be looking for reasons to eliminate guys off their lists and Blackmon's extreme home/road splits will be all many voters need to do just that. 

Now, I don't think a player's home/road splits SHOULD affect an MVP vote, but they do. I mean, if it's really given to the most valuable player, that player is the one who helps his team the most and when you play half your games at home, what you do at your home park is obviously extremely valuable to your team. Nobody criticizes Aaron Judge for using Yankee Stadium to his advantage. But there is so much bias against Coors Field hitters in the national media that practically speaking, Blackmon doesn't have much of a chance. I'll be much more upset if Arenado has yet another outstanding year both offensively and defensively, with minimal (relatively speaking) home/road disparity AND on a winning team, and voters still find a reason to not give it to him.