Canada

right, you said it was stupid because:

Just imagine that you're in a conflict, then the enemy hacks your command and control systems and disables/hijacks all of your aircraft. Yeah, that's pretty dumb.

I'm saying that scenario wouldn't be possible. for the enemy to exploit a backdoor like this, they'd have to either:

1. break the encryption (quantum computer, classical sub-exponential discrete log or factoring algorithm.)
2. break the protocol or encryption (unlikely, since it'd be simple, the NSA is full of competent cryptographers, and they'd probably formally verify it to EAL-5.)
3. steal the private key (most likely imo, but the government also safeguards the nuclear codes, and it's hard for me to imagine F-35 kill switch keys being more dangerous than those.)

I don't think any of the above are very likely, or at least not likely enough to outweigh the strategic benefit of being able to ground your enemy's air force in the (hitherto unlikely) scenario one of the US's customers became its enemy. so I don't think it's stupid, and I don't think I straw-manned you.