Maybe Elon Musk should have spent more time in Mykonos? The world’s wealthiest man might have learned something useful about European politics — inveigh against what you will in a bar or at a beach, but unless you are a European citizen, sometimes it is best to not wade in too deeply. Consider the commotion over Mr. Musk’s suggestion that Germany’s best hope is its rightist party, Alternative for Germany party, or AfD.