Earlier quoted context omitted.
On the other hand, it's perfectly reasonable to remove some disruptive individual from a lecture (think someone repeatedly shouting the name of a soda in order to disrupt the lecture, not an invited speaker). This is the same sort of removal of ideas from the marketplace that you are talking about, it's just probably not one you want to use as a test for what you have articulated.
The two are fundamentally different platforms. Twitter is an open space provided as a free service to the public at large, while a lecture is a fundamentally closed platform (only the lecturer speaks) only open to those enrolled in a specific class. That said, even in the example you give it is not always considered appropriate to remove people causing disruption. Consider, for example, a conservative speaker giving…
What about a public park that has gotten ruined because someone keeps on doing donuts with their motorbike on the grass? A library whose books keep on getting ruined by certain people?
Even public services need to have some maintenance to not fall apart. There's a reason we call 4chan moderators "janitors".