In free countries, the owner of the phone should have a right to have or not have any features they want on their phone. The fact that Google and Apple don’t respect your rights doesn’t mean that those rights don’t or shouldn’t exist. Almost anything can be used as a weapon.
The US has complex export laws that prevent the shipping of technology to hostile countries that can use the technology in weapon systems. Perhaps we can put kill switches only in CPUs that are shipped to Iran and North Korea and other hostile countries. That’s about as aggressive as the restrictions should get.