Mathews: In Los Angeles, I went to find a riot. Instead I found a quinceañera.

On Saturday, I went to a riot and found myself at a quinceañera.

I wasn’t lost. I had headed to the L.A. County cities of Compton and Paramount to see the “riots and looters” that Donald Trump and his administration were talking about on social media. I know those communities from years covering them for the Los Angeles Times.

But I couldn’t find any rioting.

Yes, Los Angeles County Sheriff’s deputies were on Alondra Boulevard.  The sheriffs had two lines, blocking off a stretch...