What 'Godwin' himself had to say: https://www.washingtonpost.com/posteverything/wp/2015/12/14/...

  First, let me get this Donald Trump issue out of the way: If you’re thoughtful about it and show some real awareness of history, go ahead and refer to Hitler or Nazis when you talk about Trump. Or any other politician.

The Holocaust wasn't a sudden event. It was preceded by a steady breakdown of protections and social norms -- see Night and Fog laws, Kristallnacht, etc. There's a lot of history before it came down to concentration camps, and it started with things like attacking the press and clamping down on visas.