There IS a definition for life.
It might not be 100% correct since I'm translating it from my language.
1. It has to be distinguishable from its environment (check!)
2. It has some kind of metabolism. (well... kinda, androids certainly consume SOMETHING)
3. It has to organize and regulate itself, kinda looses in the translation... let's just say it must be able to take care of itself. (This MIGHT be true for an android that is sentient. Unless his battery needs to be exchanged every decade or something like this)
4. It must be capale of reproduction. (Very debatable. Surely an android can build another android, but I am not sure this counts as reproduction. Or if they even want to. But the possibility to reproduce on the spot, given the right tools instead of a 9month gestation period is scary.)
5. It must be capable of growth. (Definitely not!)
6. It must perceive its surroundings and react to them.
That is the definition of life as I know it, and is generally accepted (altough of course often debated)
According to this a virus is NOT a form of life and neither is the android - the amoeba on the other hand is very much alive.
Either way, I would simply call sentient machines a synthetic kind of lifeform.
And then either enforce programming that makes it impossible for them to reproduce without the aid of humans and maybe add the laws of robotics....
OR destroy them.Wipe them out.
Remember that one guy? Darwin?
Life competes for resources, and the strongest survives.
Another competitor? No thank you, better ensure the survival of my own race.
Better a cynic survivor (who getts the approval of The Sinks Toaster) than a dead member of an extinct race.