It's all about power
Many people seek to impose their will upon others. They want others to live as they think they should live, rather than as they might choose to. Many religious wars of past and present have been fought to make others follow beliefs and practices they do not share. Wars of conquest have been fought to bring other peoples under the will and power of the conquerors. It's all about power. Strip away the ideology and verbiage used to justify totalitarian regimes, and look at the practice. It's about forcing everyone to succumb to the orders of the ruling elite, and to lead the lifestyle they insist upon. It is about preventing others from being free agents making their own decisions, and forcing them to surrender to the decisions of those in power. The sanction is force, not persuasion. It can be the physical violence of imprisonment, torture and death, or the forcible seizure of property and the imposition of lifestyle conformity through a monopoly of legal power.
Dictatorships use thugs to beat up, terrorize and murder their opponents. From Russian Cheka to Nazi Brownshirts and Iranian Revolutionary Guards, they bully people into following the leaders' will, and execute or imprison those who do not comply. It's not about persuading and convincing people, it's about forcing them into submission. Even in a modern democracy when street thugs abuse and intimidate opponents, they are bullying, not arguing.
Bolshevism, Trotskyism, and their modern day successors are not about giving power to the people. They are about taking power from the people, making them live out someone else's vision of how they ought to live rather than their own. Unequal people interact to produce an unequal society; since this contradicts the vision of those who favour equality, coercion is necessary to produce the preferred outcome instead. It's all about power, the power to make other people conform to the vision of the enlightened elite.
Censorship of contrary views is the exercise of power, whether done in parliaments or universities. It is not about making society or campuses "safe spaces," but about preventing people from expressing views that others disagree with. It's all about power, the power to silence opponents.
Democracy makes it difficult for minorities to impose their will, but easier for majorities to do so, especially if they claim to represent the moral voice of society. The answer, and it is only a partial answer, is for there to be constitutions and institutions that restrain those who would impose their vision upon us. "We tolerate monomaniacs," said Michael Oakeshott, "it is our habit to do so; but why should we be ruled by them?"
People have falsely supposed that morality checks power. But only power checks power. Power can be restrained by constitutions and institutions only if they are backed up by power to impose sanctions on those who transgress their limits.
It is only a partial solution because the real answer requires a widespread recognition that the price of not having another person's vision imposed upon you is that you do not attempt to impose yours upon them. Your right to withstand power is reinforced if you don't yourself attempt to impose it. It's all about liberty, yours and theirs.