I may lack sufficient context and experience with his 'work.' It doesn't make sense to me that a guy with a multi-million dollar/year media business that transacts purely on his personal brand would be serious (or, specifically, be serious in public). I'm not in his head; I could definitely be wrong.
Media = WSJ and other professional media that hopped on the WSJ story.
Haters = Consumers of the WSJ story who took it at face value and used it as an opportunity to bash "YouTube stars" in general and pile on Pewdiepie specifically.
I remember playing SOCOM on PS2 back in 2001 and people saying tons of deplorable stuff given the novelty of anonymous voice chat. I think it'd be weird to believe that every one of those things were said perfectly seriously and not for pure shock value ("trolling"). I think it is possible for someone to use the N-word and not be racist.
The fact that he called some faceless Caucasian video game avatar on a screen "n****r" proves my point in a way. Based on what we know about this guy, do you honestly believe he'd call an actual black person that, or even a black videogame avatar?
That's definitely their right. In this case, they probably should. He fucked up.