I'd swear the caustic banter with the butler has more chemistry than the main relationship does.
@viirlin: I read it if anything as a homoerotic joke rather than a homophobic joke, FWIW. (Fujoshi-bait, not gay-shaming). I mean, joking (or even sincerely assuming) that he must be gay and in the closet because he's shown great disinterest in women to date, isn't really indicative of homophobia. It may be a bit cavalier, and dismissive of people's right to just not be interested in anyone, but that's another thing entirely.
It's not like the butler said or implied it would be bad if his partner were gay. Honestly from here he looked like he'd probably roll with that just as well (that is to say, over-amusedly and with sarcastically exaggerated reactions, regardless). Though my interpretation of the character could be wrong, of course.