Or maybe it depends on whether the institution is public or private. UPenn is a private university, and so the ACLU has nothing to do with it.
From the ACLU's position statement on "speech codes" on college campuses:
"The First Amendment to the United States Constitution protects speech no matter how offensive its content. Speech codes adopted by government-financed state colleges and universities amount to government censorship, in violation of the Constitution. And the ACLU believes that all campuses should adhere to First Amendment principles because academic freedom is a bedrock of education in a free society."
I don't know why they don't try to sue for infringing on their civil rights. Seems to me if a group or person prevents someone from speaking, unlawfully, that should be unconstitutional.