So when will the day come,

When programmers aren't needed anymore and we just tell robots to do the programming? If I were you guys I'd be scared for your jobs. If you don't have a job, then these robots would make your existence pointless anyway.

I could also postulate that a rock is untrollable by the fact that it cannot reason
Fair enough, let me elaborate. An AI that is deemed to have independent conscious thought, that is unable to be trolled.

anything that reasons is ultimately susceptible to trolling.
Just because something does not exist yet, does not mean it never will, people a thousand years back probably thought we'd never go to the moon. Well, most of them.