It's proof by contradiction. He's responding to somebody saying that Bezos is not a monster (because) he is just responding to market forces. But if you follow

It's proof by contradiction. He's responding to somebody saying that Bezos is not a monster (because) he is just responding to market forces. But if you follow that logic, neither is a contract killer. But a contract killer is a monster. So, by contradiction, Bezos is not acquitted just because he is responding to market forces.