He's a true believer in white nationalism. And he's not strictly wrong, either. In a world of Might Makes Right, the uncontested heavyweight champion can and does have a "right" to send in the goons, because there's no countervailing force.
Miller's got the reins of this monster and he's outspokenly using it in a way the advisors for Obama and Bush and Clinton admins were more sheepish about. But you're foolish to believe the Bin Laden raid into Pakistan was any less internationally criminal than the attack into Caracas. It was just more politically palatable. In the same way, the US support for the overthrow of Assad and the installation of form Al Qaeda in Iraq leader Ahmed al-Shara and our proxy war against Yemen has absolutely been "just about the oil" passing through the Suez Canal.
Miller's committed the unspeakable crime of saying the quiet part out loud. And his voice is annoying to listen to. But he's not breaking from our international policy in a material sense. He's just coming at it like he's six whiskeys deep at the Klan Rally rather than four martinis in at the Yale Business Club.