I agree that a player bringing personality to the ball park isn't a bad thing, but at the same time, you can have panache while not being a douche. I really think Barry Sanders is the best example of a player in any sport that just got it. He let his long touchdown runs and what not be his style points, not his mouth or post play actions.
Griffey Jr. - Panache
Ozzie Smith - Panache
Larry Walker - Panache
Rickey Henderson - Panache with a pinch of douche
Barry Bonds - Douche
Manny Ramirez - Douche
Bobby Bonilla - Douche
Phillies - Douches
We also have to keep in mind that Harper is traversing a rarely tread path. At 18 years old, he's better than just about anyone in MiLB and is damn near good enough to be a starting outfielder for the parent club. I can't imagine what it would be like to be that much better than everyone else, listen to all the crap from people that frankly, just don't like him because he's that much better than anyone else and has been hyped since he was what, a freshman in HS? Could the 18 year old show a little more maturity? Absolutely, but at the same time, I think some people expect him to be as stoic as Jackie Robinson was when he broke the color barrier in baseball. Granted these are entirely different situations, but there is some correlation in regards to the spotlight each shared sans death threats.