And when the standbys and primary instruments are all giving you the same bad information, what then?
Pitch, Power, Airspeed. You've got two, you don't need the third. I used to teach private pilot students about a hundred years ago, and before they went for their check ride I'd make them do a pattern with the airspeed covered up. It forced them to watch pitch angle and power settings.
I even had it happen to me in a C-180 that had a bug in the pitot tube a couple of years ago. I just went back to the basics - Pitch, Power, Airspeed.