You have examples of them being expelled? From a public university? For speech that was not considered a direct threat, or "fighting words"
Again, being a student is not a job.
Here's a good one for you...
Student Expelled For Facebook Posts Loses First Amendment Case Against College
Students in Minnesota, beware what you say in social media, or at least mark your accounts private: The U.S. District Court in Minneapolis
threw out a lawsuit earlier this week by a student who was expelled from a nursing program for his personal Facebook posts.
The Student Press Law Center reports that Craig Keefe sued Central Lakes College for expelling him based on posts that it said violated the school’s student handbook:
In November 2012, two fellow students approached Kim Scott, an instructor in the nursing program, with concerns related to the content of Keefe’s Facebook posts. In the posts, he addressed frustrations with other students in a class using phrases such as “stupid *****” and “not enough whiskey to control that anger.”
The school didn’t allow Keefe to appeal the expulsion, leading him to argue the school “did not give him the proper due process to defend himself because the matter was misclassified as ‘academic’ rather than disciplinary,” SPLC says.