There is no HR issue here. The student is not an employee. This is a pure free speech issue. A student may ask any question they please legally. They may even say something unpopular. This is especially true when it is about a hot political issue.
It is truly outrageous to discipline a student because he said something another student may not like.
This is a state funded school. There is no HR issue.
I only mentioned HR because I deal with similar issues within the workplace. But there’s a long ways between what you can legally say without repercussions and being able to say anything without repercussions. I suspect it’s not that hard to kick someone out of graduate program based on them having said something deemed inappropriate to another student.