I agree with you, but our bishops have shown us time and again that they're not willing to act forcefully. They'll change their tune if their brother bishops start sitting in jail.
You are very right. Mr. Mahony should currently be enjoying a stint at Club Fed. But the Church cannot try and convict someone. However, it can and should give out harsher punishments. For instance, Mahoney should have been stripped of his rank of cardinal.