The media is liberal if defined as "relating to liberalism."
Liberalism, as in, "a theory in economics emphasizing individual freedom from restraint and usually based on free competition, the self-regulating market, and the gold standard." Assuming 90% of US media exists to make a profit, then they are indeed acting in a liberal manner.
It's precisely this interpretation of being liberal that made me stop calling myself a liberal and start describing myself as a progressive. I don't want there to be any ambiguity.