Very interesting thread. When Nixon was caught covering up a crime legal proceedings were instituted at the time, as his offenses (if proved) were an abuse of office. When Clinton was caught evidently committing and suborning perjury the decision was rightly made to put off adjudicating the charges until he was out of office, so that his unique job responsibilities would not suffer. For the Pope to be brought to trial he would need to be credibly charged with a crime. I imagine that, since the Pope rarely steps down short of death, either sort of crime would therefore have to be tried while he is Pope.
However arguing that a pederast priest should not be defrocked is not a crime; that is a purely internal matter. Taking steps to conceal the crime itself would qualify - and since as a Cardinal or Bishop he had quite a lot of powerful over the faithful, it would arguably be a crime in the Nixon mold, requiring immediate prosecution.