Hard to get past how creepy and pushy the ML was at the beginning with his insistence on making the FL participate in his fantasy when she hadn't consented to it. Also particularly weird that he (and his community) seem to view the D/s dynamic as a non-romantic arrangement when my understanding is that it is very common that folks in that kind of dynamic (particularly where it's a 24/7 monogamous kind of deal opposed to a casual scene) absolutely do consider themselves to be in a romantic relationship and are very much in love.
I cannot accept this dude's pursuit when he's not romantically interested in her - so, what? She takes time out of her day to indulge his fantasies just because he wants it and can't find anyone else? I mean, in this case, the FL likes him so she's willing to try (but even that is less than the enthusiastic consent you want to see in a scenario like this), but with the info he had to work with he was crossing some major boundaries and just straight up sexually harassing her.
No thanks.