Y'know, I'm a little tired of this phrase. I'm sure there are plenty of people out there who are making a comparison in the sense of saying the policy is as bad as anything the Nazis did, which is clearly not true. But that's not what everybody is doing, what some people are doing is imagining: "what if this already bad thing is taken even further? what is the conclusion, the zeitgeist expressed here?" The world people imagine that exaggerates the political changes from a few years ago is one that seems more Nazi-like, so that's why it's expressed that way.
Just because Nazism ended up being so drastic doesn't mean comparison can't be made. In fact, that's what honest comparison sets out to do: we might say compare and contrast is a redundant phrase, because comparison highlights the contrasts, that's what good comparison does. In comparing things to Nazism we're highlighting how much things are moving in that direction, NOT saying the crimes are as bad as the Nazis. So let's not use shutdown phrases and try to pressure people from speaking about these things. Because it's good in general to avoid exceptionalism w.r.t. the Nazis, and be aware of any political shifts which could cause us to repeat the mistakes me made then.