I've never met anyone who referred to their parent like that who didn't have at least a marginally abusive family life.
It is plainly offensive to address kin as "sir".
It is plainly offensive to address kin as "sir".
You have no evidence that the GP abuses his children, or even that his children literally call him 'sir' (he may have been exaggerating for effect).
If your children respond to orders like trained animals or soldiers, they are doing so because they were conditioned to do so. I am choosing to define that conditioning as abusive because it simply doesn't happen naturally.