Unless Johnson has a ridiculously inflated ego, there's no way he took it that personally. He's an average player who's almost certainly going to have one of these careers where he plays for six or seven teams, one or two years at a time. He's probably going to get traded a couple more times. He's a valuable bench player and a useful trading chip; being an "extra piece" is pretty much is whole job.
Justin Upton was supposed to be the cornerstone of the franchise, and instead they soured on him after one bad year, blamed a lost season on him, let it be known that they wanted him out of town, and then shat all over him after trading him away. I've gotta thing Upton's revenge factor is 10 times higher than Johnson's.