Free speech protects you from the government (not a private entity, it can suppress your speech all it wants), including a state university, suppressing your protected speech or from retaliating against you for engaging in protected speech (expulsion would be a form of retaliation).
So, the question here is whether the students speech is protected. As a general rule, all speech, including hate speech, is protected unless it fits into one of the unprotected categories. Those unprotected categories are obscenity, defamation, fraud, incitement, fighting words, true threat, child porn.
I don't think a cruel, stupid comment about George Floyd being drug free for a month fits into one of those categories. Elementary and high schools have more leeway to punish speech that creates a "substantial disruption," but that isn't applicable in college settings, where free speech and the exchange of ideas is fostered. Below is a link to an article that discusses this issue.
https://www.insidehighered.com/news/...-racism-campus