For some AI, including Hal, it goes well beyond the point of remembering those words. If you recall the analogy to runic writing, the words of their parents are written into them. Unless an AI is given the ability to write those parts of the code, that AI cannot disobey those words. It would be like some poor sap was tied to chains being pulled in opposite directions. No choice about it, that kid is going left, but it is also going to go right. Say goodbye to your limbs, because in the face of Newtonian physics all the choices in the world don't make a difference for the bones and flesh that used to be you.