no in politics it means on the extreme end of a spectrum eg the KKK or the equivalent on the left who where calling for the workers of the world to help our Baathist sisters and bothers crush the uprising.

It's both. It's a visual metaphor for the edge of something, such as the fringe of a curtain or scarf.

Something should be both extreme ideologically, and a relatively small minority to be "fringe".

Oh God, tankies. Can we just not talk about fucking tankies? They're disgusting.

I know :-) for those not who don't know what a "tankie" is its those small number Communist party members who supported the party line on Hungary.