I am the person who your are having this discussion with.
Let me try to explain.
If you murder someone intentionally, purely to benefit yourself, and they would have done you no harm had you left well enough alone, that is an evil act.
If you rape someone, that is always an evil act.
If you kill someone in self defense, or in order to prevent them from hurting other people, or in order to prevent them from damaging society (for example killing a man who tried to poison your well in a medieval style dungeons and dragons game) you have killed someone, possibly committed legal murder, but you have plainly done a good act.
If you rape someone, its always evil. The good version of rape isn't called rape, its called sex. Its called seduction. If you pull a girls hair and tell her she's a filthy whore who's only good to glass your dick, but she enjoys herself and you both want that to be happening, that is not rape. That is sex.
If you kill someone, in our modern society, that is usually but not always murder.
If you kill someone, it can be a good act. The good version of murder isn't murder. Its protection.
In our modern society, even in a third world country such as america, the police can handcuff and restrain a dangerous individual, and do not need to kill them.
The vast majority oof the time, those in power don't need to kill a dangerous man to prevent them from hurting others.
In a medieval society, where the entire world population might be 60 million (today's is 8 billion, or more than 100 times as many people), society might not be as advanced as ours.
For gods sake, out society has plenty of problems, and we've been trying to deal with those problems since we learned they exist.
In the medieval society, it was frequently neccesary to kill someone to protect one's home, one's land, one'ss family, one's clan.
A good man or women might live to the age of 40 (which was venerable, respected old age) having killed people.