Really don't get why this makes him a "douche". He isn't trying to stop the other guys from getting nominated. He's just saying he is happy with the band he is with now and doesn't want to detract from that by doing something with the 'real' GnR.
Then again, people probably would call him a douche if he did a proper reunion as well, saying he's only in it for the money.
The point remains, Axl has done a ton of douchey things, but this isn't really one of them.
It is kind of douchey, to be perfectly honest. I know that he doesn't exactly have the best relationship with his former bandmates and hasn't for quite some time, but he's making this all about him whether he thinks he is or not. It's not all about him. It's about G'n'R, collectively, and their accomplishments as a band. He should be able to rise above the fact that he has some ill feelings toward his former bandmates and accept this prestigious honor. Instead, he's choosing to be petty and selfish.