I wasn't around for that thread, but it still lives on the board.
That said, it's not perfectly analogous or really on point -- the comparison of LeBron to a message board weekender. He's world class. Gold medal. NBA Finals champ thrice over. Finalist even more times (nine?). He's proven that at the top of his profession he's the King of everything and dominates the league. He may be the best basketball player to ever play. He's at least in the top ten. To insinuate that he's not mentally fit to play is really a broad shot at the toughness of the NBA.
So I'm not sure what LeBron has evinced through his litany of runs through and deep in the playoffs that he doesn't have the mental makeup to play a different sport like football. Yes, we know football is tough, but athletes at that world-class level can certainly rise to different expectations if it is required of them. LeBron, by all appearances, is a bright and thoughtful individual that would likely pick up on the nuances of football.