I'm sorry you feel that way.
First of all, a photo contest has nothing to do with "handicaps," so I'm sorry you feel that's relevant. I doubt anyone knows from the photo that Dudley is or is not handicapped in any way, so I seriously doubt that was an issue.
Secondly, entering the contest didn't harm you in any way, except perhaps to get your hopes up of winning. Nobody criticized anybody's dog, there was no entry fee, and it was clear by the $1 million award that there would be lots of entries and so a slim chance or winning (regardless of what tactics people decide to use). So why will you never enter another contest? Are you that disappointed that you don't want to risk losing ever again?
Again, I'm sorry that this contest upset you and that you were disappointed by the outcome. I agree, it probably could have been better managed. But are you really angry at the management, or mostly just disappointed about not winning?
If you really like this forum, personally, I think you should get over your anger at dog.com and stick around here. 
Or, if you're truly upset and don't want anything more to do with dog.com, there are plenty of other good dog forums on the internet and you could probably be quite happy at one of them. If you google "Dog Forums," the result that comes up below "community.dog.com/forums" is a popular board with members and former members here, for example.
I guess what I'm trying to say is you shouldn't let disappointment over a contest cause you so much unhappiness. I bet if you either move on and "forgive" dog.com or move on and find a different forum, either way, you will feel a lot better. And certainly Dudley doesn't want you to be unhappy.