That violence is not a “bug” of Leftism, it is the beating heart of Leftism itself! There simply is no Leftism without at least threatened violence. And often it is not just threatened…
Yes, the Left are (obviously) the theoretical heirs of National Socialism, and the violence and force and intimidation of the Gestapo is quite naturally inherent in Leftism.
Those who are Conservative, OTOH, value freedom and moral agency. Taken to an extreme, it is Libertarian in nature. Conservatives value persuasion and conversion, while Leftists hang their hat on coercion and the lack of moral agency.
Indeed, the lack of moral agency is the defining characteristic of Leftism. Leftism is, at base, a distorted, deformed, evil parody of moral agency.