1977. Rooftop. Breaking Dawn. (Sorry.) As the sun rises, it shines down on a sleeping Damon and Lexi. Even though she's been a vampire for longer than the Chucklehead Brothers, you'll recall Lexi doesn't have a daywalker ring (which, really?), so when her flesh start to sizzle, she wakes and rushes to the shaded door, but can't open it. Damon sits up and says, "Good luck. I spent all night reinforcing it. It was tough. I had to be really quiet, not to wake you up."
Okay, how did he reinforce the door from the other side of it? Lexi's less concerned with those logistics and wants to know what he's up to. Damon says, "Payment [...] for the last six months of my life. For the nagging, for the self-righteous platitudes. I'm paying you back for six months of you."
Lexi dons the Captain Obvious cape. "Your humanity isn't back on, is it?" Damon smirks. "It never was." This was all just a joke, a big fat lie, and the best part is that she believed it. "You thought I was like Stefan -- a wounded little bird you could nurse back to health." When he strokes her cheek, Lexi grabs his wrist, but that doesn't stop Damon from taunting her. "He's a victim. I choose to be this way." He pulls Lexi's hand out of the shadow and lets it burn. Screaming, she pulls it back in. As Damon leaves, he says, "Enjoy the day. I hear it's going to be a scorcher." Oh, Damon. Haven't you done enough to her? Must you pun at her, too?
Present. Night. Rooftop. Elena: "So you pretended to have feelings for her, just to get her off your back." Damon says he was willing to do whatever it took. "Sound familiar?" Elena's tone is mocking. "Aw. I hurt your feelings." Damon says he's not worried about his feelings. He's looking out for her, because someday, the switch will flip, and all the bad things she's done will haunt her. Elena: "So you're saying you felt bad for Lexi?" I think she means "about" not "for" because Damon says, "She became a walking, talking reminder of all the awful things I'd done. I managed to avoid her for decades, and then she just shows up in Mystic Falls to wish my baby brother a happy birthday. And BOOM. A rush of memories. A rush of guilt." Elena: "So you kill her?" Damon says, "Out of sight. Out of mind." Off Elena's incredulous look, he adds, "Every day that you're like this is the day that you might do the one thing that you take back."
Elena says that since he spent six months setting up Lexi just to hurt her, he was being spiteful, malicious and borderline evil. "And you say that you had your emotions turned off. But those all sound like emotions to me." Damon is too polite to outright correct her that those aren't emotions (joy, sorrow, fear, anger, etc.), but rather adjectives that described him. He just slips his correction in. "Maybe they were. Maybe hatred was the first one I got back. All the more reason to cure you. That way we get the normal Elena back, without all the ugly stages in between."