Seriously only an asexual could be that calm.
Kishi even emphasizes this by making Suigetsu gauge Sasuke heart rate, which was unaffected. Instead Sasuke doesn't blush or smile or get a nosebleed or send any message that his mind is in the gutter. A healthy homosexual teen would be excited by that, this is a fact. Ironically the same evidence that convinces me that he's not 100% gay is his infamous scene with Suigetsu. I personally believe he has no sex drive but is still capable of love. Even the kiss between Sasuke and Naruto wasn't meant to be taken seriously. I'm not completely oblivious to say that it's never been implied, but there's more evidence that Kishi does it just to toy with yaoi fans. So it would be safe to say that he's asexual. At this point it is a fact that he hasn't shown that kind of interest in boys or girls.