A "human life" is a human being. That should've been simple enough for everyone to understand. A zygote, blastocyst, fetus, etc. are mammals at early stages of development, and we're discussing humans in particular here.
And I said "innocent" for a reason. Self-defense is ethically defendable, for example, as are certain types of war. Unfortunately, sometimes violence is needed on a practical level to protect life and society against aggressors (from the level of out of control individuals like murderers and rapists to unjust governments). But that should ideally be a last resort and violence should never be initiated against the innocent and vulnerable (young children, the elderly, handicapped, etc.). I believe society should protect the most vulnerable among us.
There's also more extreme interpretations where only total pacifism is allowed, but I don't see such things as workable.