We cannot continue to treat all offensive speech acts -- intentional or not -- as equally blameworthy

Whether she meant to do it or not, the student invoked a well-established concept derived from the realm of torts: strict liability. Strict liability applies to inherently dangerous activities, like speeding (not knowing the speed limit won't get you out of a ticket), using explosives or husbanding dangerous animals. Even if all proper precautions are taken, if a construction blast injures a pedestrian, in most states strict liability assigns fault to those responsible, no explanations or excuses.