I cannot tell you how many get removed for the various reasons, nor can I tell you how many choose to leave voluntarily or somewhat involuntarily. However, you might recall that in America we live with the assumption that people are innocent until proven guilty and that it is better to let a thousand criminals go free than to punish an innocent person. I submit that the system is set up to work within those assumptions.
For example , cadets who are members of the Cadet Honor Committee investigate and try other cadets for honor code violations. However the dismissal authority for an honor violation is the Secretary of the Army, a political appointee. Make your own judgment.
Here is a counter anecdote to your story: At his 40th USMA class reunion, a retired colonel asked whether he would have time to get to the cadet bookstore to buy a copy of a certain book. The reason he wanted this book was because he had borrowed a copy of it from one of his classmates while they were still cadets and had failed to return it. Since he knew this classmate would be at the reunion, he wanted to be sure he could return the book. I find that to be a rather strong expression of duty and honor--the first two words in the USMA motto. YMMV
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