This was written on the occasion of my daughter's admission to graduate school at a major state university.
The terms 'liberal' and 'left' are not interchangeable. 'Liberal' is an old-school term denoting a school of thought on one end of the political spectrum, with 'conservative' on the other end. In this old framework, you could say what you thought and so could the other guy. You could disagree vehemently, but you could also "agree to disagree".
The Left, however, does not tolerate dissent. Conservative speakers are increasingly not tolerated on college campuses, simply because of their message. They can be shouted down or intimidated in various ways to silence and suppress the expression of their views. This behavior goes against a crucial pillar of American democracy, namely, freedom of speech. But the Left doesn't care.
Why don't they care, you ask? I think the basic reason is that their ideological framework has changed. Society has always had a division between those in power and those not, and there has been continuous tension between the legitimate and illegitimate use of power, the use of power of oppress vs its use to provide order and suppress wrongdoing. A person was understood to have an identity which was individual and not purely dictated by membership in a class or subgroup of society. There was also a notion of truth, in which differences could be discussed and adjudicated.
What has changed is that the Left understands social dynamics primarily in terms of power, and one's identity is based almost completely in one's membership in various groups. Certain groups in society have power, and they wield it over those without power. You are an 'oppressor' or 'oppressed', and there seem to be no intermediate categories. Oppression can come in multiple, intersecting forms via discrimination; for example, a female black lesbian is triply discriminated against, by being a woman, black and a lesbian. This understanding of the compounding of discrimination is called 'intersectionality', and it appears that a person is completely defined by this. The great task of society then is to bring down the oppressors, which, by the way, are white straight males.
It is one thing to be against injustice and seek to help the oppressed, but quite another to adopt an ideology which demonizes those in power or those who have benefited from those in power. It is perpetual class warfare. When the oppressed get power, will they not oppress their oppressors? I'm sure of it, based on history. One big irony in all this is that, if it is all about power, then it really doesn't matter which side you pick. You might as well be an oppressor. There is an implicit appeal to a notion of justice, that injustice and oppression must be stopped; yet that notion of justice is pulled from thin air or, heaven help us, from religion.
Sexuality and gender both play into this as well. To make it all work, it is crucial to add another premise. The premise is that gender is a social construct and is independent of biological sex. On the one hand, males and females exist in a continuum, and some distinctions really are rigid and wrongly stereotypical. On the other hand, humanity is bimodal in a statistical sense (there are two humps in the distribution, not one). This point is strongly denied by today's society. If you completely decouple sex and gender, then it makes complete sense to demand that someone address you as a woman if you perceive your gender as such, but are biologically male. The thing is that you can't fully decouple them.
My best example and metaphor for why I believe this uses the idea of hardware and software in a computer. A computer's software determines the behavior of the computer, but is constrained to work within the limits of the computer's hardware. You can program a computer to do anything at all that the hardware will allow, but there are some things the hardware will not allow. Similarly, you can change behavior or dress and take hormones and mutilate your body, but you will not have changed your DNA, which will strive relentlessly to express itself in various ways consistent with your sex. The machine at base retains its hardwiring. To say these things openly at a university these days however is blasphemy, by the way.
The ideology I've been outlining functions very much like a religion for its adherents. It presents quite a complete, comprehensive worldview along with plans of action to advance it. This, I believe, is the basic reason the Left doesn't tolerate dissent: simply, other views violate their (new) religion. The new religion seeks to banish "binary" thought, and this is seen particularly in the question of gender/sex, where one sees a profusion of sexual identities, with the result that the basic male-female 'binary' sexual distinction is swept away. This is a major step away from Christianity. For, in Christianity, the binary sexual nature of humanity is instituted by God at Creation, and God Himself is the ultimate binary with respect to His creatures; that is, God and what is not God are eternally and ultimately distinct. This makes Christianity an undesirable and highly negative religion for today's world.
In the book of Acts, the Council at Jerusalem is described. This council concluded that non-Jews did not have to adopt Jewish laws or customs to be Christian and added only the request to "remember the poor". The care of the poor and needy was an established part of the early church and contributed greatly to the spread of the church. In today's evangelical church, in my experience, the poor are not well remembered, and this is a valid criticism of the church. The Anglican church does better in this, by the way. Similarly, the church has at times kept women from legitimate roles and contributions, and we should seek to recognize and rectify this. Yet, this is not the same as opening all roles to women, though some will dispute that. So, we can admit the faults and shortcomings of the church without buying into the monistic trap of the non-binary advocates, and we can seek to do better in helping the poor and needy but without buying into the framework of intersectionality.