I think OU should expel the student, not merely the sorority!
I support those young ladies right to be stupid, classless and insensitive.
The sorority is a private club. If you break the rules of a voluntary association, well, them's the rules.
They paid their money to the school. The school accepts public funds and should support and even defend their right to say unpopular things.
There is no problem with free speech. Only tyrants and dictatorships have a problem with free expression that does not cause or threaten injury or harm.
What you said is literally too vague for me to actually retort. I can think of all sorts of situations where free speech is absolutely necessary to being able to even consider yourself to not be a slave.