Since you don't know anything about the doctrine and why we claim certain things that you point as "mind manipulation", I'll try to clarify some things.
1. Jesus died for our sins because God's people, Israel, was living away from God once more. His figure and his salvation had been announced by the prophets for centuries, but specially by the "Servant of Yahweh" chants of Isaiah. The ruling chaste in Israel, the jewish priests, and the people didn't understand anything, because it only could be understood afterwards, under the "Light of Christ", as the apostles and the disciplines did later. After His death and Resurrection, we are saved, because we know that if we believe in Christ, we know we'll participiate in His Resurrection.
2. For jewish, the fact that God came to Earth to be humilliated and killed has always, and still is, a scandal. A tremendous one. It is, actually, the reason why they killed him, quite a paradox isn't it? Therefore, it's very difficult for the jewish people to convert, although the apostles as St. Paul and St. Peter tell us in their letters had a remarkable success there. For the rest of cultures, however, it can be more easy to understand it, since we can look at History of Salvation from outside, and with a full perspective. All the Old Testament is announcing, is a preparation of the coming of Jesuschrist, by Whom God would save the world and stablish the New and Eternal alliance.
It's not brainwashing, it's a matter of faith but with so many proofs that once you understand them (for example, how come 4 people wrote the Gospel, in different places and time, and the same story?) you can't do but believe.
The matter if you adhere to the Catholic, Orthodox, or a Protestant Church is different, though.
