> That's not what I see happening, but sure, you can accuse other people of that if you like.
I've seen videos of it happening. Basically a speaker is invited to give a talk, but people who disagree with her crowd the auditorium and scream to prevent the talk from being given. The intention is not to "engage [or] defeat on rational grounds," but to shut down and exclude.
A lot of the people who have this done to them are in fact disagreeable, but that doesn't make the reaction less illiberal.
Fortunately, Ann Coulter or someone has plenty of outlets for her speech. And we've come a long way from Governor Ronald Reagan ordering UC Berkeley to cancel speakers because he didn't like what they had to say.
How have we “come a long way” from Reagan doing it? No-platforming actions don’t require the backing of a democratic majority. A few self-righteous people get going and no one wants to burn political capital objecting. Making the disinvitation button available to a wider population isn’t progress.