That's not completely true. They do dance on the precipice of authoritarianism and balance on the slippery slope towards totalitrianism but there is some distinctions between Right Wing Republicans and Fascist like the Nazi's.
First, though extremely authoritarian, right wing conservatives are more autocratic then totalitarain. Fascism/Nazism is totalitarianism. What makes most American uncomfortable with this is that Authoristarianism gives lip service to our liberties while systematically degrading them to further empower the State. Most people also know that the road to totalitrianism leads through authoritarianism. Right wing conservatives would be more at home with a divine right monarch, then a secular Dictator with absolute powers or a liberal republic with limited powers for that matter.
Secondly, fascism and totalitarian States replace religion with "The State" where as right wing Republicans prefer to nationalize a specific religious belief. They would be (and are) appaled at the idea of replacing religion with a belief in the State. In either case, both point of views are extreme ones and essentially deny others their religious liberties including the right not to believe or practice a religion.
Right wing Republicans have not condonded violence as a means of achieving their political ends at least domestically that is.
However, there are some similarities that right wing republican do have with fascist/Nazi's.
The identification and marginalization of a specific group of people as a threat to the State (for Nazi that was the Jews. For right wing Republicans that would be Liberals, Blacks and Immigrants).
Intolerance within the political framework for dissenting views.
A wide spread and comprehensive political propaganda network that glorifies nationalism, exagerates threats to the nation, specifically identifies groups of peoples as a threat to the nation and marginalizes those who dissent as treasonous. The similarities between US right wing media (Fox News, Newsmax, right wing talk radio) and Goebbels propaganda model are not superficial or coincidental.
Like fascist/Nazi's right wing Republicans marginalize intellectuals as being elitist. This is understandable and those who are educated are the most likely to communicate the failings and lies of their political movements and are therefore a grave threat to their political movement.
Bigotry. Right wing Republicans prey upon the ignorance of the poor and uneducated by manipulating their racial and ethnic bigotry. The Nazi's exploited anti-semitism and racial hatred of ethnic Slavs. In the US it's southern conservatives and their bigotry and fear toward Blacks. Can anyone doubt that this is the ultimate factor behind the motivations of people like the Birthers? With more and more assimilation of Blacks into the American mainstream this misquided bigotry from conservatives is being placed more often on Mexicans and Immigrants though a healthy fear of Blacks still exist in most rural and southern white conservatives.
