Like bittired, I also found Frey's Prime Directive not quite right, but for another reason. Thomas Frey criticize our current views regarding the future as being too dark and dangerous and for all that he comes up in the end with "preparing our resolve for struggles unimaginable", which is not (in my book) something put in a brighter note. A message having a little more hope and longing for the better (but not necessarily easier as I agree that life should not be easier), will be more appealing and more in place.
I think the prime directive stated is a little too long and lofty. Instead how about: "Love or die"?
To not go extinct?
If that is the prime directive, we're doing a really poor job at it. We haven't even gotten off the planet and we already have started to deplete resources we rely on and either ignore or deride those that provide us with food while we live ridiculous lifestyles whose primary purpose is to consume and pretend to each other how great we are on a multitude of lit screens in unsustainably growing suburbs and cities.
Yes, that is a prime directive for us as animals, as simple beings. Thomas Frey is looking for a prime directive for us as humans, a directive for our additional potential and capability. In the general context of us as beings, Thomas Frey's searched directive could be called "secondary".