Dean was right, of course. Sam had run away from hunting because of a girl. Dean, it could have been argued, had also run away, two years ago, because of a girl.
The difference was, of course, that he had tried. Tried to raise Sam, tried to bring him back. As Dean understood it, Sam hadn't tried at all. Sam had run.
Well, in reality, of course Sam had run. Back when Gabriel had been messing with his mind, when Dean had died over and over, Sam had finally snapped. Finally ran.
Except that Sam had run to hunting. He was as bad as soulless and later suspected that during that time, his soul had at the very least been stifled—when Dean dies, a part of Sam dies as well, he supposed.
What had really happened during that year was a bit different than Dean had assumed. Sam had tried to get Dean back, he really had. The problem was that he tried too much. The drunk escapade into Hell where he rescued Meg, for example, and the very sober flee from it. He had a few monster hookups that kept him posted and had become allies with the very beasts he had grown up killing, by the end of the year, which Dean would have never allowed had he been alive.
So of course Sam said he had run and never looked back, of course he said that he'd actually taken Dean's words to heart. Because even Dean's reaction to that would have been better to his reaction to why Sam had George the Leviathan on speed dial, and why he had not taken the phone that Kevin had called on (because the phone had too many memories, Sam knew).
Dean had gone to Purgatory during that year.
Sam had gone to Meg.