On 'Liberal Fascism'

The charge that 'liberal' and 'fascist' are interchangeable isn't a true one; but it has 'legs' ... which is to say, it sounds truthy to a certain audience. I wonder why that might be? I wonder if it has something to do with the social reality implicitly acknowledged by left-wing, and broadly airbrushed out of right-wing, political philosophies: that living in 'society' entails duties and responsibilities to other people. What I mean is that various right-wing positions, to various degrees, aim to shrink or minimize the notion that we owe any duties to fellow human beings (by, for instance: severely limited who gets included under the rubric 'fellow human beings' to exclude, as it might be, foreigners, other races, other sexual orientations, poor people and so on), reaching a vanishing point with those versions of US Libertarianism that deny the individual has any duties or responsibilities to anybody but him/herself. Liberalism, in acknowledging the counter position, in effect says: the teenage fantasy of absolutely untrammelled individual liberty is a lie. I can see how a malevolent perspective might spin that as 'fascism'.