There's also the much more important fact that "The left" believes these ideas have already been sufficiently litigated.
Would a church congregation happily bring in speakers to talk about why allowing abortion is necessary medical care? They probably would be unhappy if a church did that more than a few times, since most american christian faiths claim to have a "definitive" answer on things.
Or should Universities also be expected to platform people who would openly advocate for reintroducing slavery to the US? Would people really be happy with that? Or advocating to remove the voting rights of women? Some republican politicians openly tweet that women's suffrage is a bad thing.
Would you, as a university student, be happy if your university brought in someone who gives a two hour speech about how 2+2=5? What if that same person was adamant that anyone who doesn't believe 2+2=5 is the "enemy" and wants to hurt america?
What about that time a bunch of kids in South Africa (I think) held a "Safe space" group activity and decided to talk about how math and science is colonialist? Should we encourage such useless discussion at our colleges?
Remember, these are the same colleges saying there's no money to give to better or more professors, so if they are the ones putting up the speaking fee, that feels pretty fucked up as a student.