Your example of driving privilege is inapt. My hypothetical privilege to drive is not rejected based on my ability to take care of myself. It is rejected on my ability to take care of others around me.
I think that's exactly the point the parent comment was making: that, as with driving, an individual who is unable to take the wellbeing of others around them into account can/should have their privilege of individual autonomy restricted.
Obviously there's a difference between defecating on the sidewalk and recklessly injuring someone with a car, so the question becomes how we define harm.
Obviously there's a difference between defecating on the sidewalk and recklessly injuring someone with a car, so the question becomes how we define harm.