Not sure I'm remembering well, but I believe there were hints that VIKI might not bound by the Three Laws? Not necessarily explicitly, it could be implicit as she is an A.I. with access to it's own code or at least with capacity for learning (which basically should be the same thing).
The Three Laws are perfect, at least from programmers' POV. It's a set of simple and well designed
if... then commands. No machine cannot exceed it's code, so logically, no robot can violate them. Only time when that excess happens is when there is a bug. But, usually, a bug ends with a crash...
Lanning is aware of the omnipresence of VIKI and by extension of USR management, which makes recording the message so much difficult. It was VIKI, not the robots, that were the enemy, and Lanning knew it. If I remember correctly the image has very telling facial expression when this part of the message is played back. I propose that Lanning was aware of the potential VIKI had to overcome the Three Laws' limitations (by both being advanced positronic A.I. and central management unit for the USR robot population. I think it was not pride, it was resignation.
It is only when The Three Laws are put to interpretation - especially through moral aspect - then they become insufficient. Ironically, anything that involves involuntary sacrifice on the part of human being is by definition amoral, so this is where my bottom line came to be, because VIKI's interpretation destroys mankind, leaving in place human species neutered at the very least, creating herds of mindless bodies in result.
This whole issue in the movie comes from the fact that it is, actually, based on a work of another writer and only when movie was being made, the decision to tie it to Asimov's Universe the Three Laws came to be, consequently needing them incorporated into the plot somehow.
And the problem comes from the fact that
The Three Laws are basis of the positronic brain design and violating them results in self-destruction of that brain. We also know that it is impossible to build stable positronic brain without The Three Laws as stated - EVER -
so this is why this inconsistency in the movie causes problems.
In other words, plain old movie plot hole.