With all due respect, I can say this. Many people do stupid things-- like drink too much or smoke pot. The issue here is in this situation is that he did not say, "you know I had a drinking problem in high school that caused blackouts and I stopped drinking that heavily. I have learned and not done that kind of drinking or behavior since." This is about honesty and integrity. No one on earth is perfect but it is not so difficult to take responsibility if he might have done it. However, if he maintains his innocence and a full airing of the events occur, well then, he has taken responsibility.
You are right many exemplary people did awful/stupid things in their past, including forcing people to have sex or attempting to force someone to have sex. Is it in the past? Yes. Was it right? No. The test of people is to hear them admit, take responsibility, and make amends. Unfortunately, many people who drink too excess in high school don't remember the things they do.