General computing platforms, in which you can run arbitrary unsigned code without violating the warranty, exist. In fact, Apple has a major business in manufacturing them (MacBook, etc.)

This could fly for iPad, the iPhone they can make a case it jeopardizes the reliability in contacting emergency services.

Overall this will go over most law makers heads because they are technically incompetent.

To a degree they could (although it'd be quite embarrassing for Apple to claim that their OS can't prevent apps from damaging phones), it could be somewhat similar to how Android manufacturers sometimes handle custom ROMs by having the unlock set a permanent flag somewhere. Doesn't necessarily give them an out of legally required warranties.

Yes, which is why they should be mandated by law to include them anyway. Maybe that will force them to figure out a better security strategy.

I don’t think our current law makers are technically competent enough to understand this.

In a theoretical anti-trust investigation wouldn’t that been seen as extremely anti-competitive?