I admit I'm a dolt, what is the feminist message that everybody thinks

I think the message is not to manipulate.
PJ and Ruth basically tortured each other using the only things they had in the hut.

Ruth is vulnerable after being deceived by her family and being led into to captivity (I'm not talking about the peeing scene, I mean with the screamin in the circle). She is a head strong and assertive woman but even the most indpendant person can have the wool pulled over their eyes eg. dad pretending to 'die' and being promised a plane ticket back to India after the 'decoding' even though the family have no intention of buying the ticket.
It's clear to see Ruth doesn't wish to go in the hut but because she believes that PJ won't 'break' her she decides to ride it out (no pun intended).

PJ is confident and slightly arrogant, in my opinion, in his perception of how he manages to control women using sex and also of how strong women are in general. Such as the situation with Yvonne: he asks her personal questions and makes her feel unwanted after her 'affairs' so he regains control again through sex and manipulation.
PJ is slightly insecure in his skill of decoding as he says he needs extra support and when he lowers the tone of his voice as he asks for carol to come out to australia, thsi could indicate that he is ashamed of asking a woman for help which in turn could trigger his low opinion of women.
He almost patronises Ruth when they first arrive inside the half-way hut because he wishes to keep her sweet in order to make his job easier. He tells her she is her own person yet contradicts the statement by suggesting that her thoughts are not hers and are, again, controlled by a man, Guru BaBa.
He takes away her shoes and sari (Is that how you spell it?) which is again another way to control her and cause Ruth to feel vulnerable.

After forcing Ruth to watch the cult videos, i think Ruth is even more detirmined to prove that she is in control of her own mind but that doesn't mean to sya that she probably hasn't thought about whether her faith is a cult or not; I think she does this when in the bathroom crying, perhaps she is thinking of ehr next step then?
She plays the damsel in distress, knowing that PJ will definately gravitate towards this. Now to the peeing scene: it could be interpretted in many ways such as submission, arousal, possibly fake arousal to entice PJ into Ruth's control, releasing inhibitions and showing herself in an outwardly vulnerable state when inside she is quite strong- the list of interperetations is endless.
The morning after Ruth plays mind games with PJ by teasing him as to whether she enjoyed sex with him, whether she pretended to be vulnerable or whetehr she was telling the truth. She can see that he is weakening and resists displaying how vulnerable he is aswell. She kisses another woman to make him jealous and succeeds but goes too far and soon becomes in danger when a group of men take her away and undress her onyl to be rescued by PJ.
When Ruth 'teaches' PJ how to please her, he is bowing to her authority but also she is giving him a slight sense of limited power as he si the one pleasing her, not the toher way round.

As both characters' faults are exposed, both are revealed to be equally vulnerable and equally powerful at the same time. PJ realises just how he treats women as objects and that perhaps he should not feel ashamed of a woman's equal superiority to a man. Ruth has been extemely cruel to PJ and in general was quite cruel in the begining when she mentions how she will see her dad 'perhaps next time in the next life'. Her faith is based on being kind but Ruth was so wrapped up in proving everyone wrong that she sort of lost track of the real meaning for a bit.
Both relaise how manipulative they've been and I think this is where their love for each other comes from as they bonded over the 3 days and spiritually grew too.

However, the whole of this could be completely wrong so don't take my word for it.