If people go to a media source with the assumption that they're going to be receiving useful information about the world, then I'd consider it a self-evident ba

If people go to a media source with the assumption that they're going to be receiving useful information about the world, then I'd consider it a self-evident bad thing for the media source to lie to them and give them information that isn't representative of reality. To put it into machine learning terms, giving people a bunch of training data that is biased (i.e. isn't sampled from the same distribution as reality) is going to train people's judgment to be less in tune with reality. I don't think I need to argue the laws of the US to make this point, but the press is free to be biased (up to a limit, remember that!) because excessive legal attempts to curtail media bias can tend toward making things worse -- simply putting the people in power in charge of doing the biasing.