No there isn't.
The fandom of an investigator is an issue? Are you really impugning the integrity of someone that you have never met and know nothing about?
Here's the thing - who do you think actually knows more about what happened between Hardy and Holder - someone who interviewed witnesses and actually spoke to Hardy and his attorney, or a fan of the team that Hardy is signed to play for, and has read news articles? The decision made here was born of PR, not bias against the Cowboys. The conflict of interest? Doesn't exist - it's the figment of people wearing tin foil hats.
I suppose Darren Woodson tried to screw the Cowboys throughout his career, as he grew up a huge Pittsburgh Steeler fan, and loathed the Cowboys.
Or, perhaps his fandom is irrelevant to what actually occurred.
No matter the uniform that Greg Hardy was slated to wear this year, this was going to be the result. The NFL was going to make a decision based on winning a PR battle so they can look like they are tough when it comes to domestic violence. That's why they did what they did with Adrian Peterson (BTW, how did Mara or the Giant fan have bias here - Peterson plays for the Vikings). Hardy will appeal, and it will be reduced. I would expect that he will be on the shelf for between 2 and 6 games.