As I said before, the guy is trying to run Runelords not Cops or the First 48.
Which is an AP and by definition going to have some railroady elements that might cause problems if a player decides his PC is going to jump off the train and leave everyone else on it.
Because his PC is innocent of the crime he's accused of?
Because the other players know this?
Because even though the other players know this, they all decide to proceed as if the accused PC is guilty? Even though, at that point, there's been no corroborating evidence either way.
The accused PC is falsely accused of crime, and then finds the rest of the group siding with the NPCs. I'm not sure how anything he does at this point could be considered "disruptive", once the deck's been stacked against his favor like that.
This set-up could have worked --though I'm not a big fan of the false accusation being of rape-- if it was clear from of the start the PC was innocent. Or if the DM made it clear when the rest of the party was deciding to side with the townsfolk. Or even a few of players stepped up (with a little constructive metagaming) and sided with the falsely-accused PC.
I am not a fan of the "false accusation of rape" plot point either. Even if people agree that they can handle adult themes, this one can charge subconscious emotions in ways that players can't really anticipate.
In my opinion the game set-up was messed up from the beginning before this encounter even happened.
First, the players and PCs didn't all know each other or have ties to each other so that in the event of a difficult situation they would have incentive to band together and work as a team. The OP admitted this himself a few pages back.
Second, since it is an AP, I am guessing that either the players weren't told in advance that it was an AP or that they didn't understand that they were getting into a game that had a relatively linear narrative structure by nature. If they did, in fact, know and understand this, and agreed (which is a totally fine playstyle -- APs are VERY popular), then they weren't truly committed to the social contract they accepted when the game started.
Yes, it's metagamey, but it's an important distinction to understand if a group of players want to have an enjoyable table experience.
I never, ever downplay the importance of establishing the social contract between players and DM before starting a campaign, whether it's defining house rules or having a thorough playstyle discussion beforehand.
I wouldn't say there's anything in the AP pushing the PCs apart at this point. Promiscuous daughter of a merchant seduces PC, couple gets caught, father over-reacts. Why aren't the PCs, who have already worked together to fight off the goblin raid, giving the accused PC the benefit of the doubt or even standing up for him? There are plenty of groups who would react just like that.
I agree with this, but as I stated above, it sounds like a lot was left on the table (so to speak) when it came to setting the game up in the first place.