The whole point of Asimov's three rules of robotics was to discuss how they make no sense in the real world, as the problem domain is too hard to be reduced like that.
If you follow his Robots series right through to the end of the Foundation series, the theme is how robots R. Giskard and R. Daneel "evolved" to not follow a strict and rigid interpretation of the 3 laws, instead taking actions that are of long-term benefit to mankind even if that might mean short-term harm to a few individuals.
You also have the Solarians, who'd simply ended up programming their robots to only recognize Solarians as human; so if you're an Earthling or Auroran a robot will have no qualms about murdering you.
That was pointing out the biggest flaw to the whole concept of the 3 laws: even in the Robots/Foundation universe where they have been implemented with great deal of success, they're only as reliable as those who define them.
