my cage, I should be able to pass on the shoulder because I'm narrow enough to fit in between the car and the concrete barrier?
That's not equivalent to lane splitting... but many places in the USA specifically open the shoulders to traffic on high congestion days for the same reason California, the UK, and other places allow filtering.
As for the rest of your post... you are making a mistake: you are arguing against facts. It is a fact that filtering reduces congestion. It is a fact that filtering is safer. You can't "not buy that argument" because it isn't an argument...it is something that researchers have proved. You *can* argue that some other good is important enough to override that fact. I won't agree with you, but at least you will have a leg to stand on. Let me recast this in a different context. It is a fact that vaccinating young girls against HPV, a sexually transmitted disease, will reduce their likelihood of contracting HPV and experiencing the various side effects including cancer. You can't argue against that fact, but you can argue that vaccinating young girls against sexually transmitted diseases will reduce one of the barriers to sexual activity and cause an erosion of morals which is worse than having women contract HPV and die of cancer. You see the difference? You don't dispute the fact because facts are facts... you dispute the worth of those facts in relation to some other goal.
Now, to address some of your points.
How is passing someone in another lane disrespectful? Cars on highways do it all the time, even in congested conditions. Lanes almost always move at different speeds, and part of driving on a congested freeway is sitting in the #1 lane while the #2 lane flows past you 5mph faster than you. Filtering is no different... the motorcycles simply pass in a parallel lane... one which is made up of the unused space between stopped traffic.
As for whether more people could ride... more people are riding simply because of higher gas prices... that says that people can be induced to ride if presented with practical reasons. Saving time is one of the practical reasons. This isn't speculation... people in California (such as myself) are induced to ride because of the time savings.
Ride it like you think owning it matters.