18th Century French politics has nothing to do with it... and for the record, I'm not a monarchist. It's really very simple:
1.) Nazis are Totalitarians.
2.) Totalitarianism is a sickness of the Left.
People like you (and Hitler, when he was alive) are confused because you believe that anything you disagree with must come from the other side of the ideological fence. At some point Hitler said to himself: "Y'know, those darn Marxists and Jews are all Left-wingers and I really don't like them very much, so I must be Right-wing." Your "thinking" is probably along those same lines: "I'm a liberal and I disapprove of Nazism, therefore Nazism must be Right-wing" It's not unreasonable, but it is completely wrong. The ideological positions of Nazis, Communists, Islamo-fascists, etc. has nothing to do with what you or I think of them, but rather with what they think about the Individual vs. the State. That -- not who sat on which side of the chamber in 18th Century France -- is what ideology is all about.
Let go of the nonsense you learned as a child and think for yourself.