The NRL's "smoking gun" is a line in a report that says Brett was ejected for being intoxicated. I understand this is disputed by the Manly club, but even if it were true, bouncers are not known for getting these things right all of the time and it is hardly conclusive evidence. I know plenty of people who have been kicked out of pubs after having one or two drinks (or sometimes even nothing to drink). It is established that Brett's diabeties can contribute to the appearance of intoxication, which would be another reason why a bouncer could have erroneously considered that Brett was intoxicated.
The problem is that Manly and Brett did not have an opportunity to properly defend these allegations because the question of Brett's intoxication was a key issue at Brett's trial. Manly and Brett may, quite rightly, not want to reveal their full defence to the NRL as it may compromise their ability to put forward the best possible defence at Brett's trial. A four week suspension is a big penalty, but it is not worth risking a jail sentence to avoid it. Gallops supposedly comes from a legal background and he should have known and understood this, and this knowledge should have been sufficient for him to overcome the pressure from the media to suspend Brett and wait until the outcome of the Court case was known.
The other potentially much more damaging consequence of the NRL's decision to suspend Brett is that it clearly had the capacity to prejudice Brett's trial. If you were on a jury member at Brett's trial, where one of the key issues is whether or not he was intoxicated, would you consider a finding by the NRL (apparently after an investigation) that he was intoxicated and a 4 suspension imposed on him lead you to believe that it was likely that Brett was intoxicated? If you didn't know how incompetent the NRL was, perhaps you would.
The fact is that the NRL should have reacted to Brett's case in exactly the same way as it has reacted in relation to Benji Marshall. The NRL should impose heavy sanctions any player found guilty of assault or sexual assault, but when a player is facing allegations of that nature, the last thing the NRL should be doing is taking any action that would make it more likely that the player would be found guilty.