No...Yukki's slowly sinking into the insanity. He was laughing while he shot the people around Minene.
It could give a new kind of light to his character.
And about his friends. He still cares about them, but I'm unsure for how long. Yuno's actions were for saving Yukki's friends.
Anyways, a katana's in Yuno's hands is more devestating than a lightsaber!:p