I think that’s a gross oversimplification of the history of political violence in Weimar Germany. Much of the Nazi’s rise to power in Weimar Germany came from their paramilitary forces, the SA and SS. The state was unable to control or suppress those forces. Most other political parties had their own paramilitary wing, including right wing parties besides the Nazis and left wing parties like the KPD and SPD. Left wing parties unilaterally standing down their paramilitary forces while other parties didn’t wouldn’t have prevented the Nazi rise to power.