Marcuse wrote in the 1960s that the only way to prevent another Hitler from rising is to give the left free rein and cage and muzzle the right. So by extension, anyone who supports rightists being able to spread their ideas freely, let alone implement them with real political power, is a fascist in effect even if they disclaim identification with Hitler's or Mussolini's political philosophy.
I think the other way to say this is every time the right is given free reign to implement their ideas with real political power, they end up implementing fascism. Therefore, we might prefer to temper that by not allowing them to have free reign. This does not imply giving the left free reign (as you could say the same about them), as there's ample room for consensus under this model.