Obviously, when making an argument, it is in one's best interest to make their argument logically solid and not engage in arguments that your opponents will not take seriously. One way to lose credibility in your argument is to invoke Godwin's Law, which says once you've made a comparison to Nazis in your argument you've lost your debate, namely because you're out of ammunition and are using the extreme violence of the holocaust to bolster your claim.
But what can you do if someone is doing something that is quite literally something instituted by the Nazi regime? Your objective is not to incite emotion from your opponent, but merely to say "Nazi policies revoked the rights specifically targeted at source countries and specific religions. This proposed policy does the same."
I'd like to make the comparison because it is factual, strongly correlated both in deed and in motivation. It's not "You know who ELSE breathed Oxygen?! HITLER!"