> Because first they'll come for the contractless?
No, but census data were extremely useful in organizing the holocaust.
> Why is it some people are incapable of discussing Germany without tiresomely invoking the Nazis?
Because in these cases that's how the political discussion in Germany in the 1980s/2000s went when the above-mentioned measures were discussed. It's simply the benchmark our governments are judged by. The Nazis are not some boogeymen that you use whenever you need a politically correct movie villain, they were the democratically elected government of a first world nation, and should be treated as such.
More generally: Governments should not operate as efficiently as possible. They should be easy to keep in check by the population.