Hating Kaname just because he's a love rival is just a pathetic excuse. T_T The guy isn't bad, so give him a break just because he also loves Yuuki - long before Zero, might I add. If anything, Kaname's love for Yuuki has withstand a lot. I'm sure Kaname knows the danger of Zero as his rival but his action towards Zero has not been anything but courteous, even when Yuuki isn't there.
Another thing, I've read posts where people are saying Kaname is selfish. Seriously, what has he done so far that is selfish? All his scheming I find has been for protecting Yuuki, his clan, and the pacifist treaty. He gave blood to Zero (his rival), he told Zero to protect the woman he loves when he could not (now for a guy in love like Kaname, that's saying a lot), and despite his vampire guardians around Kaname does fight his battle alone (ie. Rido) trying his best to protect Yuuki from it.
The one most selfless thing Kaname has been trying to do was let Yuuki live as a human, so as to save her from the tragic fate of a vampire, the horror of her past, and to fulfill his promise to her parents. It must be extremely difficult for him because he knows that this way he may lose her. But because of Rido and circumstances he had to turn her back to a vampire. Although he rejoices that she is now back at his side, I'm sure he feels regret and guilt for having done so. That's why Kaname had such a sad expression during the scene he turned her back.
Some may mistake Kaname's cool, aloof interaction with Yuuki as indication that he doesn't love her as much (hell, some even went so far to think that he's using Yuuki
) but a misunderstanding it is indeed! Kaname avoids revealing his feelings for Yuuki and become anymore intimate because that would raise others suspicion of Yuuki, which may lead to those other vampires uncovering the truth about Yuuki and their past. Kaname's action is all to help keep their past a secret but even then they still suspect - after all, a guy as much in love as Kaname can only be so "cold" to the object of his desire.
Zero needs Yuuki, that we can obviously see, but what has Zero offered Yuuki in return? Kaname also needs Yuuki as the only woman he has ever loved and he has done a good deal for her already.
I'm not saying Zero is bad (I like the guy almost as much as Kaname - just that I want Zero to get his ass in gear and do something about his situation) but I'd just like to say that Kaname has so far been unfairly judged.