Why Does Ivan Deny the Beating is Evil?

In After The Ball, by Leo Tolstoy, the main character, Ivan, falls in love with a beautiful woman and meets her father, a Colonel.  Hours later, he witnesses the savage beating of a Tartar, under the direction of the Colonel.  Even though Ivan felt ill watching the beating, he couldn't recognize if it was evil or not, at least not right away.  What are the reasons why?
     He liked the Colonel and thought he was a good man.  That made him look for reasons to explain away his actions as acceptable.  “Obviously he knows something that I don’t,” he told himself.  “If I knew what he knows, I would understand what I saw and it wouldn't torment me.”  (187)
     Because of the environment he was in and the people around him, Ivan was more inclined to convince himself that what he was seeing was not evil.  The soldiers, the Colonel, and the people watching all seemed to agree that this was necessary, or at least felt they couldn't stop the beating, that it had to happen.  “If it was done with such certainty and it was recognized by everyone as being inevitable, then it follows that they must have known something I didn't,” he thought (187).
     Probably if he had decided it was evil, he would have immediately realized that the Colonel and his daughter were people he didn't want in his life. And though over time, he let go of her, it was hard for him to accept right away.