So what? If you have a sense of humor you can't be a winner? Josh Donaldson used to prank teammates - was he not a winner? I agree with you that teammates should hold each other accountable, but I also think that's better done in the clubhouse, not on camera.
As for the Yankees... f*** the Yankees. Maybe they didn't accept losing, but they still seemed to do it pretty well last year. Need more stiff upper lip!