I think the homosexual trait in CK2 needs to be looked at in a broader context than that of Catholic values. For many cultures and religions the main question was not "are you diddling boys" but "are you neglecting diddling women." Greeks had an attitude of "boys are for fun, women are for heirs", which was widespread across the middle east and some pagan cultures.
I don't know specifically enough about Viking approaches to the matter, but in this case your spymaster liked to run around the castle in ladies' undergarments chasing the stable lads, and your ruler just thought he had a nice butt after those long intrigue briefing sessions. I think the modern application of "bi" would work, but I'm rather sure peoples of that age didn't bother with the distinction.
--Khanwulf
