FWIW, things have gotten safer for motorcyclists since those guidelines were published.
Many local stations/newspapers ran the story in different forms for several weeks. They ran them again at the start of summer. Drivers have been more courteous about leaving gaps and not intentionally closing off the gap to block motorcyclists.
I have seen CHP pull over assholes that do it for the first time in 20 years of riding.
We can't have a discussion about passing a law to make it legal because of the non-motorcycle riding publics ignorance about the subject, and the behavior of the "loud pipes" and squid riders who spook drivers when lane splitting.
The broader public has no idea how it is done in Europe, the traffic jam reduction it provides, or the fact that Motorcyclists are at their greatest risk in stop and go traffic.
It really boils down to "they cut in line"... as if that were anything but an emotional argument: you can cut in line too buddy, ride a motorcycle. (Which the wife/SO won't let them have, most likely... bitter clingers)
Bikes are like rocket science... except we try to avoid the coming back down part.