[He does like her. There is virtually nothing that he wouldn't do to keep her safe and content. He also knows that he can't love anyone in this prison as wholly as he would like to because, inevitably, they'll leave each other. Chekov and Lucy were in love, but he still wasn't willing to give his universe up to follow her to hers. That—the knowledge that duty will win over a romantic relationship as much as the parting itself—has made him reluctant to try again. No one deserves to come second to duty.
Kitty certainly doesn't. He can want to kiss her and hold her and love her all he wants, but until he's willing to give up everything, it's not good enough. She wants to be with Reid, and maybe Reid can give her everything.]
I can talk, okay? [He gives her a squeeze.] That was a very good kiss, but so long as you're still my friend, that is all it needs to be. I'm happy with that. Are you?