It was an example of a tolerant campus, where a burgeoning pro-Palestinian encampment might be left alone even as student protesters were arrested across the nation. Free speech would be supported as long as things remained peaceful, officials said last week.

But by Wednesday morning, the peace at the University of California, Los Angeles, had been shattered. The university canceled classes for the day, pushed back midterms and scrambled to address an overnight eruption of bloody violence…