Why do conservatives think there are/were no right wing dictators?

That's a nice ...whatever you call it but you miss the point. Hitler was indeed "right" as you call it but to think the right of Nazi Germany is the same as American republicans, you are so off base it's not even funny. Germany had the left (communism) or the right (socialism). Our definitions of left and right are not the same as the rest of the world and you should know that.