Isn't it too much of a convenient coincidence to say that it's impossible and also immoral to rationally understand something?

analysis of relationships - which, to me, have always been emotional, passionate moments - by talking like a machine about optimal universes and utilons.

If explicit analysis of relationships would completely ruin the joy they bring you, then it is rational not to analyze them. However, for most people who've embarked on such analysis programs, this does not seem to be the case. The more important something is to you, the more vital it is to optimize for its good characteristics.

I sympathize with your distaste for taking apart love to see what it's made from, but that's the same frame of mind that refuses to put a value on human life, and thus ends up wasting large amounts of it by making scope-insensitive decisions. Refusing to analyze love might similarly waste large amounts of potential future love.

to the author it only extends to the "us"-group and not to the "them"-group.

The PUA experimenters here have noted that modifications of the standard methods may be necessary to appeal to the "rationalist" crowd. But I feel confident that none of them would claim Evolutionary Psychology doesn't work on us. I think you see as a lack of empathy what Lukeprog sees as analyzing everyone equally--sort of the "don't anthropomorphize humans" approach.