He can't still go to events to report on them? Or even set up interviews with fighters?
He loses special access, which he had obviously abused, but his ability to report on the sport is effected in no way.
Any journalist nowadays depends on content to stay afloat. Not just stories, but content in general. MMAfighting.com needs the access to the backstage areas to interview fighters and get the stories that they produce, stories that the UFC benefits greatly from. They also need media credentials to take pictures and video to use in their articles, because they can't just take the UFC's published pictures and use them. They have to produce their own. It's not as simple as you are making it out to be. They don't allow professional photography unless you are a credentialed member of the media.
If you think that what he did is "abuse" special access, then you've gotta have the same beef with nearly every other journalist out there, because all of them would have reported the Brock news had they received it when Ariel received it. Sure, the UFC can be annoyed by Ariel getting the jump on them and they have helped him out, but the publicity that Ariel Helwani has generated for the UFC over the years is unprecedented when it comes to a media member. The favors work both ways.