I'm seeking advice to help my girlfriend Bree navigate a tricky situation. Bree's husband, James, has a girlfriend, Sarah. Last summer, Bree and Sarah had a falling out, which eventually led to James and Sarah breaking up. Recently, James and Sarah reconnected and started dating again, but Sarah decided she no longer wants to be around Bree and wants to go completely parallel.

Now, whenever James and Sarah plan overnights at James and Bree's home, he asks that Bree spends the night at my house and not to return until Sarah leaves. This became a problem when Bree needed to run home last night during one of their dates to get some things she forgot and to drop off their shared car. She texted James saying that she needed to run home and he got upset, saying she couldn't come home. He insists that Bree can't be anywhere in the vicinity when Sarah is over because the idea of Bree being in the same house, even if they don't see each other, makes Sarah uncomfortable.

Bree wants to accommodate James, but she feels like he is displacing her from her home and prioritizing Sarah's comfort over her own sense of home and security. Bree asked if she was being unreasonable, and I told her she has a right to go home and be in her house. It seems more reasonable for James and Sarah to have overnights in a neutral space if Sarah is so uncomfortable with Bree's presence (though Bree pointed out that getting a hotel room or Airbnb for James and Sarah's date nights is not currently within their budget).

Bree decided to bring this up with James today, but he was very insistent that asking her for space on their dates is reasonable and normal for parallel polyamory. James is very much on the spectrum and can be rigid and unyielding regarding rules and expectations. Bree asked me to help provide resources to back up what she's saying to show James that his expectation isn't reasonable and to offer alternatives to forcing Bree out of her house.

Any advice or help provided here would be appreciated.

Edit - For additional context, I consider James a friend and truly believe him to be an overall good and reasonable guy; he can just sometimes be stubborn and inflexible when he has his mind made up that he's in the right. We're all relatively fresh to poly (less than two years) so I think in this case he's under the mistaken belief that what he's doing here is correct. If anyone has any resources that I can give to Bree to pass along to him to show him that this isn't the way, I think he's capable to course-correction. We're all still learning and growing and this is just one of those growing pains for them.