That's actually not true most of the time. To be charged with a crime at all, you must have sufficient probable cause that a crime was committed. The question is, more times than not, was this particular person the one who perpetrated the crime.
That's where you're wrong.
Lawyers can't determine it. Judges, who would ultimately sign an arrest warrant, would be deciding it as well. So would a district attorney who applied for the warrant.
Again, if it's widely debatable, then there's so much reasonable doubt already that no DA worth his salt would touch it with a 10 foot poll, let alone a sitting judge.
In the end, extortion is almost always a one way street. Example: I get pictures of you having an affair. I tell you if you don't pay me money, I'll give the pictures to your wife.
What this is isn't that. It's more that they both have dirt on each other, and one is simply saying "If you don't show the dirt you have on me, I wont show the dirt I have on you."
It's not the same thing. Both parties have something to lose. It's more of a quid pro quo than outright extortion. To criminally charge over that would, in the end, do far more harm to Bezos than it would the Enquirer.