Thugs have no legitimate place in the political process. Both the fascists and the antifa tolerate (and to some greater or lesser extent, encourage) thuggery on their behalf; therefore, they are both dangerous fuckwits.
(Also, I rejected the terminology of left and right to a significant extent some time ago; it lumps looney propertarian gun nuts in the same category as fascists, and state communists in the same category as anarchosyndicalists, proving its own bogosity.)