See here, for the answer. It's being able to disguise commercials as independent news reports. Having to disclose that fake news is fake news threatens the "the free speech rights of my corporate clients" says Kevin Foley, owner of KEF Media Associates.
In the comment of that entry linked above, Mr. Foley explains that it's a "free market." If people don't like fake news, they can go somewhere else for the news. For that to happen, Mr. Foley, they'd have to first know what the fake news is.
Which is why the Center for Media and Democracy is such an invaluable resource. Ethically challenged individuals like Mr. Foley defend lies and deception on the grounds that it's free speech. Mr. Foley, in resisting having to disclose fake news, admits that he makes money from deception, that not lying to the public would hurt his business.