The way I see it is Swifty made an event. Lots of people attended the event. So many people in one spot caused the server to crash. Server gets restarted and Swifty is banned. While I do believe Blizzard does indeed reserve the right to ban anyone for any/no reason, I believe this ban is in poor taste. He cannot know exactly how many will show up, how many people are in the zone, how many people it exactly takes to crash a server, nor the ability to force people off of a server if stability is an issue. Those figures would be held by Blizzard and Blizzard alone and so I see this whole debacle as their fault. If too many people showed up at once on a server there should have been a queue instigated even though we may hate that idea.
Also in response to the rights of others' on that server, they have a right to play World of Warcraft for the money they pay. They don't get exclusive rights to play on a single specific server. Do you remember when servers were getting upgraded back in TBC getting ready for Wrath and how old servers that got replaced with new hardware went down for huge amounts of time? That was Blizzard telling players you couldn't play on your server and we gritted our teeth and bared it. This time is no different. You can't play on that one server for all of a few minutes for the server to be rebooted.