It sounds to me like Thora approached this with a high degree of rationality and forebearance, for which she should be applauded.
It also sounds to me like the people from Moon Guard were behaving particularly badly.
All of this aside, this is a change in the game we're going to have to get used to, and should develop processes for handling when it becomes inconvenient. It's far too easy to point out people as being "other", so that we can feel better on our own. Whether we like it or not, World of Warcraft's server boundaries have become increasingly muddled since 3.1 when cross-realm functionality went live with Dungeon Finder. After that experiment worked, Blizzard implemented cross-realm grouping via Real ID, then they implemented Battletags for people who had privacy concerns over Real ID, and then they implemented Raid Finder.
While those features all occur in instanced content, it's easy to see where they're headed with this, and it should come as no surprise given the age of World of Warcraft. Blizzard has indicated multiple times that each zone in the world was designed with certain populations in mind, populations which have diminished greatly as the bulk focus on endgame and congregate in endgame zones (Shattrath City in Burning Crusade, Dalaran in Wrath of the Lich King, Stormwind/Orgrimmar in Cataclysm and now the Vale of Eternal Blossoms in Mists of Pandaria). As a result, one can largely count on finding people from other realms while they're in any place in the world except the major faction cities and the current endgame congregation points.
This inclination to say "Other servers are the problem" doesn't exist solely on Cenarion Circle; complaints about CRZ are also happening on Wyrmrest Accord's forums, and it wouldn't surprise me to find it happening elsewhere. Moon Guard gets a lot of the complaints, and I'm not sure if this is because that realm has a particular concentration of undesirable behavior, or if it's ancillary upset relating to their reputation from their Goldshire.
Either way, players are players. It's very frustrating to have RP events interrupted. It's more frustrating to feel like it's pointless to open tickets in the hopes a GM will take care of the issue. But it doesn't remove the fact that the server boundaries are slowly disappearing, and are likely to continue to do so as time moves on. While its population isn't even close to WoW's, EVE Online has managed to deal with one gigantic, persistent world for years now, and I'd like to think WoW's player base can likewise learn to deal with this slow merging of environments.
Problematic behavior lies with people, not with the realm they're from. We aren't having people CRZ'd in from PvP realms, just from other RP realms. It doesn't excuse their poor behavior.
Neither, however, does it excuse any statements anyone makes that "Oh, that <insert realm here>, you know what they're like..."