Right, basically, I've figured it out now. This might make some of you go "well, duh, that's the whole point of socionics", but I want to express it anyway.
Functional preference isn't as bad as people think. For example, in what respects are an LIE and an SLI close? Their characters could be very alike. The difference is in what they prefer. And a conflicting relationship between an LII and an SEE isn't even that bad; the Se for the LII isn't something to be feared and shit. It's simply something the LII can't dig; of course, they might really like the SEE and see them as a really good mate. But at heart, they could not have the fruitful and satisfying relationship that duality offers. That's the nature of having a dual and a conflictor. A conflictor is someone who you could live with, may enjoy the company of, but - ultimately - won't be able to have a really happy, fulfilled life with, like you could with your dual.