Replacement anxiety: White supremacist terrorism

The terrorist attack in Christchurch, New Zealand, has left 50 people dead and a lot of unanswered questions. How big a threat are violent white supremacists? We take a look at a network of museums in China trying to commemorate that country’s murderous experience in the 20th century without offending the Communist Party. And our San Francisco correspondent goes in pursuit of free stuff - a lot of it-in the Bay Area.