Your argument is not sane in a general sense. A proper formulation would be it is not NECESSARILY immoral to take a life, which I agree with. You cannot make the general affirmation of your original argument.
To condone the killing of a human being, one would need to operate under the assumption that the person's life is not their own. This assumption is problematic, as it leads towards an endless cycle of killing, as well as slavery and basically every other evil that one person can inflict on another.
This claim is purely based off of assumption, along with the consideration that even if such a poll was conducted with the predicted results, a large group that has reached consensus does not mean the answer agreed upon is correct.