Why is the phrase “Holy War” an oxymoron?

Why is the phrase “Holy War” an oxymoron?

The phrase "holy War" is and oxymoron because of two reasons. First, there is not good or "holy" war. War is something that you should avoid and not start because you think that god will praise you for killing someone of another religion. Just because someone doesn't believe in your religion, doesn't mean that their religion is wrong and that god would want you to kill them. Also, most of the religions forbid killing, but still people fight holy wars and kill people who don't practice all of the holidays or people who believe in different religions. In addition, holy describes something honored and war describes something horrible, which are opposites, which makes it and oxymoron. In summary, because there is no good war, killing is always bad, and because most religions forbid killing, the phrase "holy war" is and oxymoron.