Your statement in itself is a bit contradictory. You say that if it's all that you're exposed to it shapes what you believe but on the other hand you say that there was riots between a different political persuasions.

If Fox News was pushed upon the prison population with no other alternate choice for the people to get news then according to your own statement it would have shaped the narrative of all peoples in the prison thus not leading to riots. If Fox News was again the only option but some people believed and other people did not believe then it supports my position that those who were predisposed to believing the outrageousness of this claim chose to believe it while others chose not to.

Also keep in mind that while this is a particularly large and settlement because it is against a company other media outlets as of late have also settled for definition suits against individuals. All mainstream media seems to be intentionally polarizing and using lies to do it. Often times they back down quick enough from their lies to not get a lawsuit but it's the initial lie that they know that they told is the one that spread the farthest.