Whether or not you believe Sandusky is innocent or guilty as a whole is irrelevant to Joe. Do you believe a sexual assault happened in 2001 that was witness by Mike McQueary? I think it is 100% clear that no such assault happened. The actual boy remained friends with Sandusky well into adulthood and adamantly defending him even after Sandusky's arrest. Yes, he did eventually turn on Sandusky after he was promised $$$ by a lawyer and his career prospects were likely shot due to a DUI, but even then, he can't give a consistent story and his actual testimony at Sandusky's PCRA completely contradicted his own attorneys earlier statement.
Also, in the 1998 incident that Joe may or may not known about, the boy remained friends with Sandusky for 13 more years. He testified at trial that the incident where Sandusky picked him in the shower was the only time Sandusky ever did anything to him that seemed inappropriate. Only a year before Sandusky's arrest, the now 24 year old young man send Jerry a text that said "Happy Fathers Day! I am so glad God has placed you in my life"
Even if Sandusky is guilty is molesting some of the boys, It is clear Joe was never informed about any sexual assaults.
One problem is that there is a very loose definition of sexual assault. Rubbing up against a kid naked would be sexual assault but it certainly isn't the same thing as anal rape. It seems unlikely that MM witnessed anal rape. That would have been nearly impossible from a standing position. Besides, MM testified that the boy was not in distress.
None of us know exactly what Joe was told. We do know that JM, Dranov, Joe, Curley, and Shultz all told similar stories and MM admitted that he used soft language when speaking to Joe. We also know that MM didn't feel compelled to call the police or get the kid out of there that night.
Did C&S do enough? I don't think so. Should Joe have done more? Maybe. Did the 3 conspire to coverup in order to protect football? No evidence whatsoever.