SAN FRANCISCO -- In many of his years as a rapper, Snoop Dogg seemed to embrace guns: he was arrested multiple times for gun possession and lyrics from his songs included references such as "So Snoopy he went straight to the trunk of his car (And what he get?), he got his gun and they start running hard."

But these days, the 42-year-old star, whose real name is Calvin Broadus Jr. and also goes by Snoop Lion, is pushing a decidedly anti-gun violence message. On Thursday night, he appeared at a benefit here with fellow...