Not sure what point you're trying to make by saying we'd "love" LeBron if he'd pulled the same stunt to come here. Firstly, never woulda happened and secondly (and I can only speak for myself obviously), I'd still think the dude was a douche for doing it the way he did, but yes, I'd root for my team. I'd feel a little cheap though.
As to LeBron acting like a child? Taking a cheap shot at your former team and fans who are down in the dumps right now, then trying to say it was someone else's tweet... if that doesn't make you think of a little kid caught doing something and trying to lay the blame on someone else than I don't know what will.
I'm not saying the guy won't win multiple championships with the rest of the super-friends, and after a week my Laker hate is back and I'd probably root for him vs LA -- dude is still an immature douche though.