Yeah, it's kind of like those girls at a party I overheard making jokes about how Asian men have small penises.
I just REALLY want to be friends with them (since I'm half, they can't tell they're insulting me to my face). I am so openminded.
It's implying that I don't want to associate with people who are completely closed off to the concept of an interracial relationship, not that I don't want to associate with people who won't sleep with me.
We don't know that either of those things are part of the context of these potential restrictions though. What if they had some quasi-sensible, non-racist reason for it, like being the last of their line and needing to carry on their family? We've been told that elf+human=human and it's been implied in banter that elf+dwarf=dwarf, and do we even know if Qunari can reproduce with the rest?
I totally agree that the notion of pure preference is problematic when the different races are used as metaphors for human cultures, but if we are to take them as distinct species, that changes the flavour of the preference, at least to my mind (especially when we know that there are different cultures within each race, so we could potentially distinguish between a character whose preference is about xenophobia and one whose preference is species specific).