I don't think you looked very hard.
The
Code of Ur-Nammu, written two thousand years before Christianity was around, specifies that the punishment for murder was death. That tends to indicate that the people thought that murdering others was a bad thing. And the idea of "don't kill others who are in your social structure" is everywhere. Even animals follow that rule. Chimps, lions and many other animals that live in social units tend to avoid killing others in that social unit.
In any case, if you were right and murder was celebrated as a good thing by certain groups, how could those groups survive? Killing other members tends to reduce the population, and if everyone was going around murdering others, then they'd very quickly run out of people.
And how in the world do you figure that people are sacrificed to demon gods in today's secular society? I'm about as secular as they come, and I've never sacrificed anyone. What "gods" do you think are worshipped by secular people anyway? (Please note, the word "gods" there in quotation marks was intended to represent the nebulous idea of a god of any kind, and was not referring to the Judeo-Christian god. Sadly, I've learnt from experience that I need to specify such things, as some people here have tended to become report-happy.) By the very definition, secular people do not believe in gods.
Also, the claim that Christians don't murder children doesn't bear up to scrutiny. The American political right refuses to engage any laws that would actually reduce gun deaths, leading to countless children killed in school shootings every year.
When God created mankind, He wrote His law on our hears. The secular world calls it "conscience", so we feel guilty when we sin. That's why every tribe and people group formulated some kind of code of ethics, based on their views. The Bible teaches Christians that everyone inherited a sinful and rebellious heart from our parents Adam and Eve, so mankind is not capable of writing fair laws.
When Adam and Eve sinned, the whole of creation became hostile, savage and violent. This curse infected the animal kingdom as well as mankind. Animals don't have a conscience, they just have an instinct to survive and pass on their genes so they will turn on others in their group if they feel they're being threatened.
Not sure how you missed the fact that all of the ancient people groups became extinct, due to the fact that they celebrated murdering each other. Todays people groups are no different, we celebrate killing each other and our children. So will soon also self destruct just as every past people group has done.
Christians know about the spiritual realm, we know there are wicked Demonic Spirits influencing and possessing non Christians all the time, they never sleep or rest. This is why Christians always pray that the non Christians would open their eyes to realize that they're being corrupted, influenced and controlled by evil spirits. That's why the world is full of hatred, murder, drug abuse and false teaching in the world.
God gave us the 10 Commandments for our own protection from Demonic Spirits, who would have no power or influence over us if we didn't allow them access to our souls by breaking God's Laws. If we all put our trust in the Lord, the world would change instantly, we would all be super rich as there would be no need to spend trillions on wars, military, police, security, prisons, corrupt governments, fraud and the list goes on endlessly.
The Lord Jesus Christ said, "You can only serve one of two Masters" He went on to explain, that people who think they are free and don't serve any master actually serve the Devil because they are doing exactly what He wants them to do. Man wasn't created to be an island or autonomous creature. We were created to worship, so if we worship anything other than the Lord, we're actually worshiping idols which is to worship the Devil by proxy.
As for the second amendment, that debate has been raging for a long time now. We're not going to resolve it by debating it here, let those who are responsible for that amendment debate and change it if necessary, according to lawful procedure.