I agree with your assessment and it brought some thoughts to mind: We've seen that Brian is someone who seems rigid about following his ideology. Example: the "no plastic water bottles" even in a situation where they really needed water and were offered some by the cops during a nonstandard and stressful encounter.
(I'm talking about positive ideologies, like environmental values and commitments to live a low-footprint lifestyle, or to eat healthy, exercise, etc. Not religious ideologies or others based solely on one person's opinion.)
I've been in a relationship with someone who was strongly ideology-driven in this way, and to an extent I am as well, so it didn't feel like a downside to our relationship, even when I was pressured by my partner. I interpreted pressure or chastising by him as me being 'weak' and tempted to compromise my values, and him holding strong and supporting me in sticking with my values.
In fact I believe that kind of support is a major plus in many relationships, and that there is a gray area in the middle in terms of whether the rigid person is offering support or whether they are being oppressive and controlling. Personally I think the path to staying on the healthy side of that line is communication and respect, so that any input is known to be welcomed. Unfortunately too many people don't hold to high standards of communication or of respect, just in general and MEO/MOO.
I can easily see BL being this sort of rigid about his values, and that being the primary source of his criticism of everyone else including GP. And if GP saw BL's beliefs as worthy values, then she could have had a much harder time seeing his oppression/domination/control for what it was.
MOO and MEO