I see no reason to call for Dantonio's head here. He did exactly what you would hope once the information reached him. He cannot control what other people do, and there was no reasonable expectation this would happen to those boys.
That said, I do wish people would stop saying "young people doing dumb things." Rape is not a dumb thing like smoking pot or drinking in your dorm, it's not some victimless crime that only affects yourself. Rape is a dumb thing like murder is a dumb thing.
I don't think anyone is minimizing the seriousness of sexual assault. it is stupid for these kids with all the opportunities they have to throw it all away by committing what everyone agrees is a horrible crime.