This is what I am talking about. If you are wearing a Dom Brown jersey in 2016 then *YES* you do look like an idiot - the guy has a .246 career batting average.
Is it a pitiful attempt to "fit in" at the ballpark? Are you "supporting the team" by announcing to everyone, "I like Dom Brown, even though he sucks"? What is it going to do for collective fan morale if you are promoting a player who would actually hurt the team's chances of winning?
If you are a "fan" of a particular sport, and you take the time to select gamewear in the form of a team jersey to attend a game live, I would think, ostensibly, you are trying to showcase the fact that you are somewhat knowledgeable about the team at hand - i.e. "fanatic."
And donning a traded player's jersey to me says that you don't even know the current team roster, or much else about the game for that matter...