The benefit, one day, is if you're a criminal whose face is detected, the car doors will lock, and you'll be driven directly to law enforcement who will be ready and waiting to apprehend you.
I suspect and hope there will be some push back. Imagine a counterpoint in either a bug or malicious attack where innocent person is locked in and then driven into a lake or something.
I dont think autonomous cars should be able to lock people in. The car can report to police silently, that's fine.
No, it should not do even that. You are making an assumption here that police/government always have good intentions.
What society needs is kind of power balance: law enforcement being able to catch 98% of criminals is a noble goal, but pushing that number up to 100% is not possible in democratic society, it requires totalitarian control. That's why we need to make a choice here and oppose surveillance, event if it seems well intentioned.