On one hand, you're right.
Players should treat attacks on their events as just that. Not game-breakers, but fluid parts of it. It seems to me that the people attempting to make roleplay events in factions are overreacting to invasion. Almost like they get upset and just go "You ruined everything! This is why I can't roleplay here!" They're taking it OOCly, when they should be taking it ICly. Instead of a chance for MORE roleplay progression, they take it to be less.
On the other hand, the way that an attacker acts can hint at one way or another. If you come in proclaiming you are Scooby Doo, and you're here to solve the mystery of the stupid roleplayers, that's very meta, and breaking to the experience. If you come in as Chieftan Wanawakyaface of the Raider Tribe, and proclaim they shall submit or die, that's a roleplay experience.