No rendition of the Brotherhood of Steel qualifies as "fascistic", unless you're using such a broad brush that the term becomes utterly meaningless. Fascism as a political system requires a relatively complex society that is industrialized to actually be a THING, which none of the regions that the Brotherhood operate in qualify as. Just because in FO4 they suddenly got written as racists doesn't mean they're fascists, as fascism as a system, has little to do with race (certain subsets of Fascism, like Nazism do, but even then just because something has a race element doesn't make it fascistic), and to be frank in FO4 fear of the Institutes Synths is a rational position to take and the Railroad are a bunch of kinda ridiculous hippies who care more about Synths than their fellow humans...
The actual closest the Brotherhood ever came to being Fascistic was arguably in Fallout: Tactics, when a branch of the Brotherhood actively went on a conquering spree and forcefully brought settlements under their direct rule, but even then, it was more of a classic military junta / warlord set up than anything resembling Fascism, especially given that the Midwest Brotherhood actively integrated everyone they conquered into their military (and I do mean everyone, you could have Ghoul and Hairy Deathclaw recruits in FO:T and the main character is a tribal who was "recruited" into the Brotherhood).
Maxim was an asshole and a dictator who fucked up what was otherwise a fairly benevolent chapter of the Brotherhood in DC, but regardless of all that, they weren't fascists...
