It depends where he went.
If he played for a coach like John Thompson, Dean Smith (even though I know those guys weren't coaching then), Jim Calhoun, Coach K, etc. I think they would have helped knock some sense into him.
If he pulled an OJ Mayo, I think it wouldn't be any different.
I really think that's one of the things LeBron is missing (which he might actually get with Riley), someone that isn't trying to kiss his butt, but also commands respect.
I just think if John Thompson was his coach, I could see John Thompson calling him the next day chewing his butt out after LeBron walked off the court against the Magic without shaking their hands.
Some of the bigger knuckleheads of the recent past (Sheed, Iverson, Steve Francis) I think would have been even bigger knuckleheads without their strong coaching role models from college, and although I don't know this for a fact, I believe most of those coaches keep in touch with their players and continue to mentor them even when they're in the NBA. That's something I think LeBron is sorely lacking (oh ya that and rings

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Edit: I think LeBron would still be a big time egomaniac and knucklehead, just a little less so, and I think you'd see a little more class in him.