If Trump starts ethically cleansing America does the rest of the world have a duty to stop it?

If we believe the doomsayers on the left, then Trump is the next Hitler and is poised to ethnically cleanse America of various groups. Now I'm not saying I believe that, but I do acknowledge there's a fair few on the far right who'd be keen.

But if America does go down that line, and judging by the hate I see on GAG, we have to accept that possibility, does the rest of the world have a moral duty to step in and stop him or at least take in refugees?
If Trump starts ethically cleansing America does the rest of the world have a duty to stop it?
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