Obviously saying "Apple shouldn't be allowed to touch my device after I purchase it" as well as "Apple should be compelled to provide security updates" is nuts.
But I think saying, "Apple shouldn't be allowed to touch my device after I purchase it" as well as "I should be able to provide my own security updates, if Apple doesn't want to" is totally reasonable.
But Apple would never allow that. So allowing sideloading seems like a reasonable amount of pain Apple should be forced to put up with...