First you define the expression of ideas that you disagree with as a form of “violence.” Which means you are justified in using actual violence against those ideas in the name of self defense.
From Pete Spiliakos, When Dissent is Equated with Violence | First Thoughts | Blogs | First Things:
UC Santa Barbara Professor Mireille Miller-Young is more imprudent, but no more ideologically insane than the administration of Stanford University. Miller Young forcibly took a sign from, and allegedly assaulted a pro-life protestor at her college. The Volokh Conspiracy cites the police report, in which Miller-Young argues that her actions were “in defense of her students and her own safety.”
The professor’s actions are indefensible outside various left-wing lunatic asylums, but her principle of equating peaceful dissent with violence is not some sort of personal eccentricity. Though it eventually backed down, Stanford University tried to force the Anscombe Society to pay for ten security guards at a conference on the grounds that some students claimed that they felt “threatened” by the mere presence of a group that believes that sex should only occur within marriage understood as the union of one man and one woman. You don’t have to agree with any of the Anscombe Society’s beliefs to recognize both the bad faith of Stanford University and the attempt to incrementally criminalize peaceful political dissent. Stanford’s position was that mere vocalized dissent constitutes an implied violent threat and that the favored political activists who are hostile to the dissenters must be “protected” by force from the presence of an ideologically unfashionable minority.
Miller-Young’s violence is of a piece with Standford’s initial response. The opposition’s ideas constitute oppression within society. The physical presence of the opposition constitutes an immediate physical danger. The people who only see peaceful protestors practicing their constitutional rights don’t have their minds right. There can be no “peaceful” opposition to the priorities of the Miller-Young’s of the world. From her ideological perspective (which was also the stated ideological perspective of the Stanford University administration), she was practicing a form of self-defense. Her imprudence was that she followed the logic of Stanford University’s position to its conclusion