As the Wikipedians say, [citation needed]. Yes, Rotten Tomatoes is owned by Fandango, but they appear to be using essentially the same methodology that they always have: look at a bunch of reviews of a given movie, decide that review is "fresh" or "rotten" (which is done objectively based on the reviewers' own star/numerical ratings as much as possible, from what I can see), and tell you how many reviews they've aggregated were "fresh." What bias are you asserting? Are you saying they give Warner Brothers and Universal movies better ratings than competitors? Can you cite plausible examples? Through what devious mechanism are they subverting their aggregation system?
