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.