I have another possible view of what is going on here.
First off the U$hPA was truly unhappy with Bob K pointing out the problems with ACA at Torrey Pines - so, they revoked his USHPA membership. Effectively, in shooting the messenger, they gave motive to other U$hPA members to NOT report unsafe operations at some other HG/PG "training" facility. The old phrase "Mums the word" fits this situation well. An insurer who never hears anything bad about any U$hPA certified training facility remains in blissful ignorance - and continues to insure the U$hPA. When bad things are heard, insurers think twice.
But the above is old news. Bob's membership was revoked and then USHPA's insurance was cancelled.
In the mean time, U$hPA members have looked more closely at the bigger picture - after donating BIG money to help form the RRG. But they also began to actually THINK about why the old insurance was cancelled. The Nevada tandem crash was one event that may have contributed. But it was a one off situation. It was not some long term business (i.e., Air California Adventure) that seems to repeatedly be breaking or seriously bending the FAA tandem exemption rules.
So, here we are today. The U$hPa may have realized that some of its members are blaming the U$hPA for
NOT putting the pressure on Air California Adventure a number of years ago (before the Hamby accident) to stop activities that jeopardize the U$hPA's tandem exemption
AND its insurablility. How do you bring back (or keep) USHPA members who've now seen Air California Adventure as a threat to the U$hPA (and their perceived ability to fly)? Well, you make a
BIG DEAL out of pulling the tandem exemption from Air California Adventure Inc.
Symbolically, they've "killed" both the messenger as well as the company (Air California Adventure) that the negative message involved.
Now everyone can be happy!

And U$hPA keep members positioned on both sides of the fence.
Yea, right.
PS - Elsewhere on the web, Mark Forbes has acknowledged the he (and the U$hPA leadership?) knows about the other FAA Part 103 tandem exemption holders. Therefore, he also knows (or can presume) that Air California Adventure Inc. can/will go on operating as usual. So U$hPa's announcement about yanking ACA's tandem exemption has little meaning except perhaps as a political statement. The U$hPA is simply striking a (power?) pose.