One would have to work hard to prove they were NOT biased in the first place, or at least since 2011 when they sold out to the movie industry.
FYI, the other big name in movie reviews, IMDb, has been owned by Amazon since 1998 (color me surprised, I didn't know it had been this long until I checked on Wikipedia), and they also had their own streaming service, IMDb TV, now called Amazon Freevee.