Tunisian opposition leader Chokri Belaid was buried as a martyr for freedom and democracy in a country that is threatened with the loss of both, as an uprising against the ruling Islamist party gained momentum. Mr. Belaid’s assassination triggered a ferocious backlash against the main Islamist party, Ennahda, one that continued during the funeral Friday, attended by as many as 100,000 people. The midafternoon funeral on Friday was a largely peaceful event marred by bouts of violence – and brief periods of panic – as crowds tried to outrun billowing clouds of tear gas aimed at demonstrators and looters on...