Columbia University has asked a judge to reject a student's lawsuit alleging it failed to protect him after a onetime friend called him a "serial rapist" and carried a mattress around campus to protest sexual abuse.

The New York City university said in a federal court filing Friday that Paul Nungesser's lawsuit should be dismissed.

The German citizen sued the university this year, saying it effectively sponsored gender-based harassment and defamation of him.

The university's lawyers say the lawsuit failed to show how it violated laws protecting students against gender-based discrimination. They say permitting Emma Sulkowicz to carry out her mattress-toting project for class credit including during commencement activities was a "decision at the heart of academic freedom."

Nungesser's lawyer says the university "shamefully bowed to social pressure" and turned its back on him.