Arinnian's Problem

Previously, on rereading Poul Anderson's The People Of The Wind, I had difficulty understanding Christopher Holm/Arinnian's problem. Partly, this was because he did not state it:

"'We birds -' He couldn't finish..."
-Poul Anderson, Rise Of The Terran Empire (New York, 2011), p. 509.

He tries again:

"'Why, we...our generation, at least -'" (ibid.)

Tabitha Falkayn/Hrill has to finish his thought for him. Apparently, "birds," human members of choths, are promiscuous with, but have no respect for, members of their own species that are not members of choths but can hardly touch fellow birds. So far, Hrill has articulated what Arinnian failed to utter. However, she then tells him that he must have some idea of the cause but does not say what the cause is! This is authentic dialogue as they talk around a difficult subject without stating it plainly but it does leave the uninitiated in the dark.

Let us try to reason it out:

Arinnian idealizes Ythrians and disparages his own species by comparison;
Ythrians have sex only when on heat;
therefore, most of the time, he can regard them as pure, exalted in flight but not brought low by Earthy desires;
he would prefer if his Ythrian friend, Eyath, did not discuss her lovetime feelings with him - but, of course, he is not an Ythrian!;
by extension, he regards bird women as comrades or sisters, not as potential sexual partners;
however, Hrill is both beautiful and bird so what should he do - try to have sex with her or continue to regard her as above that?

Despite his promiscuity with other women - a double standard -, Arinnian is in the same position with Hrill as if he were in a society with a more traditional sexual morality. Before going to war, Vodan, betrothed to Eyath, spends time with a nightflyer, a social outcast whose affliction is that she is permanently on heat. Hrill suggests that Eyath would be glad that Vodan had had some fun and forgetting but Arinnian protests that she is too clean and then blurts out, in effect: so why don't you and I do it, then?

We sense the tension between them even if we struggle with what his problem is.