Think of it as the downside of the Enlightenment idea that governments acquire their legitimacy solely from the support of the governed. If the people of a nation do not approve of the actions of their government, they have both the right and the responsibility to change those actions.
Or, think of it as basic ethics: no one who eats meat can be more saintly than a butcher. Everyone who benefits from citizenship in a nation gets to share responsibility for the actions of the nation.
Once the National Socialists had achieved power, in 1933, German Jews protested the actions of their government, leading to the Civil Service law and further restrictions on Jewish activities. (At this time, there were many German non-Jews who probably didn't like their government's activities but benefited a great deal from those activities.) By 1935-36, Jews in Germany had essentially no power, either to support or oppose the government. (https://en.wikipedia.org/wiki/History_of_the_Jews_in_Germany...) Thus, those who could left.