I never took that particular line as being dismissive of Aral's bisexuality; rather, Cordelia was saying both that she accepted Aral as he was, and that his preferences didn't impact his fidelity. (Of which she had no doubt.) Vordarian, of course, was trying to make a big thing about Aral's preferences, in order to torpedo A&C's marriage. But, at least the way I read it, the only person Cordelia was dismissing was Vordarian.