If the argument is that Trump's proposal resembles Nazi proposals, and the Nazi proposals in question were mass deportation, and Trump's proposals are mass deportation, that seems like a fair comparison. Yes, the Nazi behavior escalated into mass murder, but that's not really the claim that's being made. It might be worth saying, "Hey, watch out, this is a way this sort of thing has historically gone", but obviously it wouldn't be sensible to set the bar for the comparison at proposing outright genocide publicly since not even the Nazis made that a platform issue.
Avoiding Godwin's Law isn't just about avoiding reference to the Nazis. An important component is to recognize that similarities aren't the automatic proof of evil that many people want them to be. The comparison needs more substantial argumentation behind it that demonstrates why the particular point of comparison was evil in the Nazi context, which is clearly present here: "The Nazis began by proposing mass deportation, based on xenophobic rhetoric and apparent economic threats to natives, which inspired hatred that allowed escalation to extermination when the original plan didn't work. Trump is proposing mass deportation, based on xenophobic rhetoric and apparent economic threats to natives, so we should expect that escalation is a possible outcome here."
EDIT: I guess what I'm trying to say is, assuming "Any Nazi comparison is automatically a claim that Trump will inevitably push for a genocide and that the comparison is therefore invalid because he's clearly not doing that" is falling for the same trick that people who make the fallacious comparisons in the first place fell for. You're reducing the entire historical context of the Nazis to a single fact and using that as the measuring stick for every comparison somebody might want to make. That's silly.