You do realize being "an extra piece" doesn't make it any more desirable when your employer doesn't value your service? I'd say he feels pretty unwanted as well, enough to warrant being chapped anyway.
Guys at Chris Johnson's level get traded all the time. It doesn't mean that teams don't think they're valuable; it just means that the teams want to make a move (to get prospects, all-star quality players, bullpen arms, whatever) and you have to give up value to get value. Players like Chris Johnson are like a twenty dollar bill -- steady, unexciting, easily transferable value. I have a hard time seeing why a player like him would take it too personally.
Wade is less selfish, more of a team player and an amazing shot blocker for a 2. Kobe is a better scorer and has that killer mentality that not many have.
Although I do have to say that if I were Chris Johnson, and I looked up Martin Prado's stats on baseball-reference after the trade, I would probably be a little pissed off that my team apparently thought that guy was so much better than me that it was worth giving up Justin Upton. Prado's better, but not THAT much better.