I want to clear some things up:
1. Ethics is an OBJECTIVE thing. The Bible spells out ethics, it IS where ethics came from.
God is the Father of morality. It is an objective thing.
No he is not. We make them up. We do not take women and children as plunder of war. We do not own permanent non-Hebrew slaves, AND THEIR CHILDREN.
We do not allow slave masters to give a wife and child to a Hebrew slave and when the term is up we say "you may leave but your child and wife is mine unless you stay forever".
We allow women to speak in church. We do not outlaw graven images. We allow freedom of religion.
We do not stone unruly children. We do not refrain from speaking to family members who hold different religious beliefs.
We do not kill every living thing in 6 cities because their religion might rub off on you. We would not drown a planet of animals, babies, pregnant women, or kill 70,000 with plagues, some babies who didn't deserve it.
No one would send someone to eternal torture or a lake of fire because they didn't find good evidence for a religion.
How about a god who threatens eternal torture for non-belief of a religion that looks exactly like a myth when studied?
It's all immoral by out standards.
Luckily, we decide what morals are, not some fictional evil deity written about in a book.
2. The Bible condemns ALL violence with the exclusion of self defense with life I believe. I don’t know. But I do know Jesus Christ said,
“If someone slaps you, turn the other cheek,”
He also said don't take an oath and many other things we don't follow. What you mention is one we don't follow as well. Did we turn the other cheek on ISIS or the Taliban? Do you advocate that we should have? Or do you follow our modern morals, made up by people?
Should we have turned the other cheek at Pearl Harbor? At a future attack if that happens?
3. Consent or simply wanting to do something does not make it ethically correct.
If I thought it was right or justifiable to kill someone, is that ethical?
It is considered ethical to use the death penalty by many people. Do you advocate for Osama Bib Laden to have been kept alive?
In the same way, even when fighters get into the ring to hurt the other and themselves, it is still not ethically justified.
Since we make up ethics, we find sporting events to be fair, with a commission reviewing the fight, weight classes, rules, a ref, a system of placing equally skilled fighters together.
People do hard sparring every day in thousands of gyms across the world, getting the same superficial injuries sometimes. So you would not stop it by banning competition. But if the fighters agree along with the laws and fans, it's justified.