At some point it moves from politics to history. Using facts to discuss the past is not the same as projecting what might happen in the future, or why something in the near past happened, when we don't have nearly enough data to make definitive statements on it. This lack of factual data leads to opinion holding sway, and that leads to inflammatory arguments.
Let's not pretend that we can talk about the current political spectrum with anything near the certainty and information we have about Nazi Germany, the economic policies that were involved at the time, the propaganda used, and the world events at the time.
Aside from news and politics itself, I can hardly think of anything more political than history. People with different nationalities and sometimes party affiliations usually have wildly different perception of historic facts. Whether the Holocaust happened or not is an obvious and well-publicized one (I believe it did, for the record), but there's an uncountable amount of subtler and/or less famous differences in how humans perceive history.
Let's not pretend that we can talk about the current political spectrum with anything near the certainty and information we have about Nazi Germany, the economic policies that were involved at the time, the propaganda used, and the world events at the time.