I'm also in California where it is legal to lane split. I've done it for quite some years. It can be done safely, many roads can have multiple vehicles traveling in parallel on a single road surface, whether the lanes are marked or not. However, most are idealized for the width of 4 wheel vehicles.
If it is illegal where you live, you can report the license number to the police, as their job is law enforcement. If you wish to be proactive toward the perpetrator, then apply for police training, to assume the law enforcement role.
I wonder. Are you similarly outraged when planes or helicopters fly over marked lanes of traffic?
Be sure your own frustrations of being within traffic congestion aren't clouding. It is a human trait to transfer these feelings onto others, particularly those that deal with problems in a different why than most.
I was lane splitting one day, quite slowly, and a woman shouted as I went by; "Why can't you wait?" And I thought; " Why can't you tolerate?". Do you suppose she wouldn't use another lane, if available? Or, would she stay in the lane stacked up, until it moved?
What galls me are the sport bike, tank top, shorts and sandals riders doing wheel stands on the freeway AND lane splitting around traffic moving the speed limit.
If they think their own life is worthless, how will they value yours? Life on the edge may be a thrill. But, what about what's over the edge?