My personal opinion is that we're not going to convince people to stop flying, so we should decarbonize air travel regardless of its relative efficiency.
But my understanding is that Kittyhawk etc are (at least in part) creating a new market of single-person "quick hops" within cities or metropolitan areas, displacing ground transport. Not only would this increase energy use per mile for existing trips, it could lead to a lot of new ones (e.g. making it viable to commute from far flung locations). This ramp in energy use for personal convenience seems problematic.
We don't have to convice everyone to stop flying. We can start with to convincing everyone to fly less. Decarbonise in the meantime, if you can, of course.