You may not have been paying attention, but unfortunately that's not the case.
https://www.thefire.org/list-of-campus-disinvitations-2000-2...
http://www.spiked-online.com/newsite/article/whats-new-about...
http://www.mediaite.com/online/university-president-shuts-do...
And I can link to many more examples if you wish. It's moved from "your opinion is incorrect but I respect your right to speak it" to "I don't agree with what you say so I'm denying your right to express it".
Now do you understand the problem? It's quite incredible, actually.
Please do provide more examples.
thefire.org - An org dedicated to freedom of speech on campus, founded by University of Pennsylvania professor Alan Charles Kors and Boston civil liberties attorney Harvey Silverglate.
Spiked - a 15 year old UK publication with staff from the Daily Telegraph and the Spectator.
Mediaite - a popular and left-leaning online news source that aggregates mainstream news sources.
Come off it. A browse through the links above are ample for anyone concerned about the truth.
You linked to "credible" sources, with some weird standard of credibility which I'm not even sure you believe yourself.
No one is stopping people from having these opinions, speaking about them, or teaching those perspectives. Claiming that this is a cause of freedom of information and somehow making this analogous to Galileo (it's not, not even in the slightest) is absurdly silly.
If you are looking to defend rational discourse and freedom of thought, well, you're not doing that -- leveling out everything on a no-questions-asked baseline is ignorant and becomes borderline satire of unbiased rational thought at that point.