Doesn't History proves this wrong? Hundred of thousands of Huguenots left French persecutions and largely contributed to Protestants culture. Nearly Half a million jews fled Europe before/during ww2. French resistance was largely organized from abroad. There are a good amount of Russian activists outside of the country currently. Just a few examples. As stated bellow, I understand the challenges implied by immigration. But it could quickly escalate in the US, and resisting fascism also comes with some challenges.