I don't think it's an automatic truth that a completely free and unbiased election is a necessity
the dnc's objective is to get a candidate elected. it makes sense that they would protect the integrity of the party by pushing for the candidate with the best chance of winning the general to receive the nomination
maybe this is flawed but imo this is just the dnc serving its constitutive purpose as a political party. i am not a fan of bernie's narrative which suggests that the solution here is to reform the party from within. if we are to criticize what has happened here (arguably true) then we need to direct our attention to the system itself (i.e. the existence of an electoral system which favors two politlcal parties in what is effectively a binary) rather than trying to put band aids on the wound.