I disagree.
Murder is evil. Killing someone in self defense is not evil. Killing someone like Hitler is morally good.
That said, would it be OK to kill innocents to kill a Hitler? For example, would it have been morally OK to nuke Berlin to take out Hitler (assuming the USA had the bomb earlier)? The Laws of Armed Conflict try to make sense of such things.
I tend to your side of the argument because having been in WWII and having my brother killed on Okinawa I know that sometimes in some situations the taking of another person’s life is a matter of life or death. Such has been since recorded time and even the Bible tells of God sanctioning war and death.