We might have lost each other somewhere.
I think the white court vulnerability to real love, for those that feed on lust that is, is much like the black courts vulnerability to holy symbols. It is part of their story and nothing else. It is there because humans believe it should be there and all supernaturals depend on human stories to express themselves in the real world, the reason Mab values that Grimm book so much. If there is another logic to it than that logic just strengthens the story. That is my take on both the why and the how.
That was my first answer in this thread: it works that way because Butcher says it does and looking for much depth was the same as asking why leprechauns use pots and not magic bags. There is no actual answer because it’s all fantasy.
However, I did then add an additional bit about the biochemistry of “love” and suggested that one could use that as a foundation if one were looking for logic and depth (like Star Trek with a bit of jargon, some real theory and then quasi science). If it is an aversion to a biochemical state, could this state be reproduced artificially as the person in the short story was attempting.
Then, I asked if the white court who feed on pain, suffering, etc. were also harmed by “love” or rather by the inverse of their preferred meal (e.g. bliss (in which case, they ought to avoid people on ecstasy)).
Of course, I still think it’s tantamount to the leprechaun pot question. And, yes, I got your argument on it, I just think it’s circular logic. But, on a topic like this, there is no answer until Butcher writes it in the books.