I tend to agree with JoePa -- let the guy run out the string, let the investigation and criminal proceedings take their course and then he will get what is coming to him (even if it is nothing).
What good actually comes from firing the guy now? What if (as he says) he was never told the true extent of what Sandusky had done? What if he is, basically, innocent?
Do I believe that he knew Sandusky was benging young boys? I do. Does my opinion based upon 4th hand information mean enough that we should demand the guy not coach 3 football games? I don't think so.