"Believe me, I will be fair in applying my pleading for you to not to kill each other and to keep violence to the consensual and mutually enjoyable sort." He isn't so sure about Elijah, but he does know Damon and has more than ample reason to suspect that Damon gets off on being beaten up. Not necessarily in the healthiest of ways, maybe, but he wouldn't keep doing it, if it wasn't working for him.