Such goes the typical excuse for many horrendous things we do. I stole some money, I clearly was under the impression that private property didn't exist, and thus, I thought my actions were completely and entirely justified!
A quick look at the sacrificial system of the Old Testament (or maybe just a quick look at one passage of Scripture within the Old Testament that happens to be about sacrifices) reveals that ignorance does not excuse sin.
Leviticus 5:15-19, declares,
"If a soul commit a trespass, and sin through ignorance, in the holy things of the Lord; then he shall bring for his trespass unto the Lord a ram without blemish out of the flocks, with thy estimation by shekels of silver, after the shekel of the sanctuary, for a trespass offering. And he shall make amends for the harm that he hath done in the holy thing, and shall add the fifth part thereto, and give it unto the priest: and the priest shall make an atonement for him with the ram of the trespass offering, and it shall be forgiven him. And if a soul sin, and commit any of these things which are forbidden to be done by the commandments of the Lord; though he wist it not, yet is he guilty, and shall bear his iniquity. And he shall bring a ram without blemish out of the flock, with thy estimation, for a trespass offering, unto the priest: and the priest shall make an atonement for him concerning his ignorance wherein he erred and wist it not, and it shall be forgiven him. It is a trespass offering: he hath certainly trespassed against the Lord."
So the ancient Israelites were held accountable for sacrificing for sin that they did not know they were doing, or did not know was sin. That's all for today because I have a debate tournament.