You've got it entirely backwards. In your scenario, the atheists would be risking their first amendment protections because they're the ones threatening to murd

You've got it entirely backwards. In your scenario, the atheists would be risking their first amendment protections because they're the ones threatening to murder someone. No, the parallel was accurate. The guy in California threatened no one, and his freedom of speech is on the line because other guys, who disagreed with him, committed murder.