It took him a long time to be able to be with another woman without feeling like he was betraying Claire. Even with the length of his ill-fated relationship with Peyton it didn't change anything. He still felt those pangs of betrayal every time he started to get close to another woman.
So when he and Horatio fell together in a moment of need and mutual comfort, he understood when Horatio pulled back. He knew whatever they had together was the red head's first real relationship since Marisol's death.
He took his time. He consoled Horatio when those pangs grew to be almost too much for him to bear. He also knew when the pain began to lesson. Horatio had come to him and they were able to love one another with the knowledge both their absent wives would have approved of them being able to find love again together.