There was a nice suggestion by @Hemlocke - ignore. Many people on this forum won't be able to define what fascism is (or even spell it correctly) without looking it up on the internet. The same should apply to IC - not every random zoner inRP has a degree in political science (or any education, whatsoever) to understand the meaning of such an obsolete by Discovery standards socio-political system as fascism, or, say, know who Umberto Eco was and/or his 14 traits of fascism which are considered to be pillars to identifying the system. If you character perchance knows this stuff inRp - you can of course challenge their knowledge inRp and bore them to death by proving them wrong (something that I sometimes personally enjoy to do). Otherwise, your character is free to dismiss them as idiots and not nice people and fly away or drop /1 /2. Dropping accusations of being a fascist coming from both left and right are so commonplace nowadays that they have lost their original meaning and sound rather cringe, both irl and inRP.
A more valid point, however, is that coming to a system for some activity and getting some cringe "offences" disguised as "RP" is a waste of time and boring. So people who spew this quality™ RP should realise that their actions might have consequences of people just not willing to RP with them. If you want to offend someone, either do it more creatively for the other player to chuckle at least a bit or don't use so generic and trite groundless accusations - those are simply cringe and boring and difficult to RP around.
