Informed Tankie

It's a little more complicated to argue that the free market is good for the consumer (though it can be done), but it's pretty easy to argue that government is self-interested and power-hungry.

Firstly, history. Nearly every government ever has been populated with people concerned with their own power. Even since the popularization of democracy, governments were still incredibly corrupt and did not operate out of a love for the people. All democracy really does to alleviate a government's self-interest is make charisma more important during election cycles, which doesn't do anything to shift the government's interests.

The people in the government are the same type of people as CEOs and people who run multi-billion companies. Whether they're put in power by military force, by elections, or by people willingly giving them money for a good or service in return, they are all people who are 100% acting in their own self-interest collecting as much wealth and power as possible. The only thing that elections do is make it so that sometimes, some government officials have to appear to be good (or appear not as bad as their opponent).

That's way easier if the press is under the government's control though. Now, the government could imprison anyone who doesn't talk about how nice the president is to puppies for at least an hour. Or, less drastically, they could revoke your press license if you say that the things the president is saying is wrong (and then fine or imprison you if you deliver news without a license).

In a free press though, even if all the major news sources are owned by the same people (which is a good point and probably to some extent true, though I don't know to what extent), there's nothing stopping new people from popping up and delivering what they believe to be honest, unbiased news. That won't be the only type of person who pops up, and it'll be exploited a lot, but the possibility of a good news source exists now.