He's Xenophobic.

“You know that's not what I'm asking!” Hayden hissed in frustration due to Zenos's actions of purposely avoiding his questions. He stood up and looked at Zenos's face with frustration and annoyance. “Why do you come here? What do you want with me? We both know I'm straight, can't you just let me be.”

Zenos's eyes lowered as he watched the person in front of him talk. He was captivated by every one of Hayden's actions. It was only curiosity at first, but now he finds himself wanting more from Hayden! He knew that had always been straight! He should have forgotten about Hayden already and let him be, but no, he can't. Not only that, but he finds himself looking for the person, checking his images repeatedly, his eyes unconsciously following the person; he didn't even know why he wanted to be near Hayden every time.

For someone like him with an already dead heart, he never thought he could be attached to someone he just met.