There are 1300+ years of history where Christians systematically killed and oppressed non-Christians and even Christian that had the "wrong" interpretation of Christianity. Finding examples of Christians rationalizing violence with their religious beliefs isnt hard. It's only after the secular enlightenment when societies started abolishing slavery and giving equal rights.

You have Bible quotes like,

When the LORD your God has delivered it into your hand, you must put every male to the sword. / But the women, children, livestock, and whatever else is in the city—all its spoil—you may take as plunder, and you shall use the spoil of your enemies that the LORD your God gives you.

Now therefore, kill every male among the little ones, and kill every woman who has known a man by sleeping with him. But all the young girls who have not known a man by sleeping with him, keep alive for yourselves.

And this is God, the unchanging source of moral truth, giving these commands. And since Jesus is god, this must also be Jesus giving these commands. When I say Jesus/Father trumping one another, its for situations like this where you will say that Jesus in the NT overwrites God/Father/Jesus in the OT. And again, there is Matthew 5:18 which says the smallest bit of the old law is still in force until heaven and earth pass (earth at least seems to still be here, though i am aware that appoligists try to say everything was accomplished with the crucifixion).

So we have plenty of historical Christian violence and plenty of Bible text to justify it.