We don't really know he has a heart of gold, even if it takes "The Enemy" to finally prove that he does not, or "Where Silence Has Lease" to establish him as a fricking psycho.
Well, in the latter, it's more of needing to vent, I think. Someone from a warrior race probably would get that blood lust for battle like Worf did in the holodec, and pretty much let his civilized self go wild. Picard probably knew how Klingons can become in a fight, and that's why he was concerned when Riker went on one of Worf's workouts. Why else does he do his workouts alone? Hell, we've even seen what Klingon foreplay is like later on.