Here is the link from the Star Alliance website that states that one Gold member can bring a guest (as long as they are departing on a * Alliance flight)

http://www.staralliance.com/en/trave...s/lounges.html

The SFO RCC was the busiest lounge I have ever been in. Practically every seat was taken in the place. Despite this, they should not be able to arbitrarily make up rules!