You speak of the question of murder, which is not the intention of this debate. Murder (taking a life unlawfully) is wrong, yes. How is it wrong? If everyone were to murder at the same time, there would be no one left to murder, therefore no one left to make the idea of murder understandable. This makes murder morally impermissible. Killing, however, by means of self defense is rather ethical indeed. Here's how:

1. If an agent should be taken into a situation in which their life is threatened, the one who had taken this agent into the situation has the intent of causing harm

2. someone of this intent is most likely to commit this crime multiple times

3. then, leaving this person with their life will quite possibly cause the loss of others' innocent lives.

4. Ergo, defending yourself is actually the most ethical path here

It is basic utilitarianism, look at how many people this particular agent may kill if left un-checked as opposed to the life of one murderer.

Well said, logically correct and quite likely to be a truth in and of itself.

You have my respect

But consider that the idea of mathematics having absolute truth as something entirely created by humanity. The concept of absolute truth, as defined as a truth that is undisputable, makes it very difficult to ascertain what we see as truth. When looking at things like time and math, it is quite easy to see the rational behind truth. Truth is a word we throw around as if it is easy to figure out, when in reality we have no idea if an absolute truly exists. Such as Descartes said; the only thing I know with certainty is that I exist in some manner.

This is not to say that I do not agree with our stance, but your logistical analysis is built around human construct.