Angel could have gone ahead and cut off Lindsey’s hand. He could have ignored the draw he felt to the young lawyer and assumed that all Lindsey was was a soul-sucking tool of Wolfram & Hart.
He didn’t. Angel chose to take Lindsey home with him. Chose to bind the human to him. And for as much effort as it took, Lindsey responded. And no matter what issues there might be, the two of them have formed a relationship and neither has any intention of going back.