When does media impartiality become irresponsible?

The media in many democracies tries to be impartial in its news coverage. However, sometimes presenting a balanced view of two perspectives if one is wrong, is a disservice and betrayal of the reader or viewer. Giving equal time to flat-earthers may be one of those, or to those who argue that the moon landings were rigged. So at what point does it become irresponsible to not point out that Iraq did not have WMDs? In regard to the debt ceiling? It is wrong not to point out that to refuse to pay for debts which were incurred when Congress authorized the spending, will have bad consequences, as when a homeowner refuses to make mortgage payments, or a credit card holder refuses to pay even the minimum payment.
This suggests that the media now misunderstands its proper role in a democracy. Informing the audience of opinions is not mandatory, but it is of facts, and opinions should be marked as such.