Maybe your son’s frat is an anomaly but for many frats in the country being “fully responsible for any/all behavior” typically just ends up meaning the brothers have one another’s backs and maintain a firm vow of secrecy. Frat brothers are not turning each other in for SA. It wouldn’t be such a huge problem if they did.
“Research has found that fraternity men are three times more likely to sexually assault a woman than non-affiliated classmates. Additionally, for women in sororities, it was reported that they are 74% more likely to be raped than other college women.”