Why is everybody so angry about Poopy Joe?

Okay, r/tf2 has made it pretty clear that the majority dislikes Poopy Joe, especially if he is the pyro. My question is why? I'd have no problem with the pyro being a monkey (though he/she probably isn't) and I'd like to know why you do. All I've been able to tell is that you think this because it's "FUCKING RETARDED". If it doesn't change the gameplay (it obviously won't) I don't care. Pyro is Pyro, no matter the man beneath the suit.