In one of the very early Lost in Space episodes, Dr. Smith insults the Robot, and he gives a warning that he is activating his self-defense mechanisms. I can understand the need for this in protecting the Robinsons from hostile aliens, but why would he be programmed to activate his self-defense mechanism activate when he is merely insulted? Surely the programmers wouldn't have wanted him to harm the Robinsons if they insulted him, bearing in mind the Robinsons were the only people expected to come into contact with the Robot.
Probably he has a routine that starts self-defense mechanism as a response to insults or threats because they usually comes before physical aggression.
So if we are programming a robot that needs some time to activate it's defensive mechanisms it would be a good idea to activate them on first signs of approaching violence.
Not because he has to use it against the Robinsons, just because he has to use it to protect himself from any aggresion.