People have roleplayed communists in the past, I see no reason why not.
But still, no offense, but I doubt people can recreate a white supremacist group properly on Argonath. Half of the people who wish to do it are edgy 13-14 year olds who's only excuse to be a skinhead is "white pride, blah blah, blacks blah blah" without even having a personal reason to hate on minorities etc.
If you think you can roleplay it properly, go for it.