That's maybe the most ridiculous thing I've ever heard. And saying "well they've always done this bad thing so there's no reason they should stop" is ridiculous on its face. There are countless examples in history of a company taking an action that was permitted when they were a minor player that is banned as they grow.
The fact that the US government has become criminally complicit in their refusal to enforce the Sherman act doesn't suddenly make the behavior they're ignoring OK.
This is literally textbook violation: Every person who shall monopolize, or attempt to monopolize, or combine or conspire with any other person or persons, to monopolize any part of the trade or commerce among the several States, or with foreign nations, shall be deemed guilty of a felony
You don't have to strictly have a monopoly to break the law.