Tsonga is just angry about a call during the TB of the Pekin's final.
He said that against Djokovic "his level isn't good enough" to beat him.
I don't think it is an excuse for him, just he doesn't like to lose, and you just can understand this behaviour from champions. Those guys want to be the best, and it's hard to acknowledge that you find better than you.
Tsonga seems right about one point though : if an influent player doesn't like an umpire, it's harder for his career, to be in the big matchs.
I watched the match, Novak's challenges were all spot on. Sure, nobody likes to lose, but Tsonga was an inferior player in that match. Tsonga seems to be too bitter for no reason really.