I agree that you ought to be able to sell something you legally own if you so choose and this is a shit move by Ford, but to play devil's advocate Ford owns the vehicle they are selling you and as owner they are free to sell it under whatever contractual conditions they want. If Ford said "so long as you own this vehicle you are not allowed to own any pet kangaroos" or something silly like that. I'm a strong advocate for right-to-repair and that extends to this kind of thing - "right to sell" I'll call it.
It also seems counterintuitive because if the resale market on the Lightning, for example, were to skyrocket then that's to Ford's advantage. MSRP will be under the resale market and they can sell the shit out of vehicles themselves. Granted there's a supply issue here, but they could have another production facility on backup and engage it when the resale market spikes, undercutting all the used trucks and selling a glut of vehicles on hype.
Even worse than this, I think, is the industry-wide move towards subscription services. That stuff sickens me and makes me glad I daily drive a 60. Toyota can NEVER shut off my carburetor from a satellite [shakes fist at sky].