You may not like the advice you got, but it was correct nonetheless. Once you became aware of the maintenance / inspection discrepancies, you also acted in violation by continuing to fly the aircraft. No amount of swearing, whining, pouting, self-pity, or stamping your feet will change that.
Welcome to the adult world.
All is not lost, however. Three days is not a long time. It's short enough, in fact, that you probably can avoid any repercussions if you stop flying today.
I mean, seriously, no one expects you to review the mx logs from day one every time you fly, so it's reasonable that you wouldn't notice the inspection discrepancy at first glance. What you did notice at first glance was that the aircraft was within the 100-hour window since the last inspection. And for better or worse, the DIY maintenance by the owner became legal once the A&P signed off on it.
So your choices are basically to keep your mouth shut and keep flying in knowing violation; to confront the boss and refuse to fly; to file a report with the FAA and refuse to fly; or to quit.
Rich