Does every decision you make personally in life put complete stranger's feelings ahead of your own? The vast majority of Americans will not stick with the same employer for their entire career. I bet if everyone who claims that deciding he wants to go work for a different employer is a stab in the back was asked if they have ever changed jobs the vast majority would have to say yes.
LeBron doesn't owe anyone any loyalty or to put anyone else first. I wonder how many people think to themselves when they are leaving their jobs that they should forgo their wishes because a customer might be upset that they are going to a new company. All we are are customers and all LeBron is is an employee of a company. A high paid employee, but an employee none the less. The standards most sports fan put on players are standards they themselves can't even stand up to (for the most part, of course there are exceptions).
When a player leaves a team I like I don't wish them ill will or take it personal. Christiano Ronaldo (someone else with an ego issue) left my favorite team last year but I wish him the best. If he wins the Ballon d'Ore, Champions League, and La Liga with Real good for him. I don't hate him because he decided he is done playing in Manchester and wants to go play a bit in Madrid. At least everyone knew he was going a full year before he left and he didn't need to hold a special to announce the team he was going to.
I love sports (well, some sports), but I don't cry and moan when something doesn't go my way or an athlete decides to go play somewhere else. It isn't personal, it is business. Life is way more important then sports. If we didn't have these kinds of over-reaction when an athlete (or any celebrity) does something the garbage that sites like TMZ or shows like Access Hollywood spew wouldn't exist.