It is not too difficult to visualise oneself being willing to kill in defense of one's home.

Suppose your country, suppose the USA, were invaded by some other country, and the US government was gone, leaving everything up to the citizens. I have no doubt but that we'd take to the hills and into the inner cities, practicing guerilla warfare. We might die individually and in droves but we wouldn't give up. We might not be able to drive them out but we could sure make life miserable for them.