We in the RP community have, as a necessity, rarely shirked from using headcanon. There are many examples of this, such as Caldari honorific -Haani: Entirely unsupported by PF, it is still accepted as part of the State's culture by most and used by a sizable portion of Caldari RPers. Ideas such as these, if accepted by the community at large, do an excellent job of increasing the depth and thus immersion of New Eden's 'backstory'. But not all such ideas, such claims, are used for benign purposes.
It isn't at all uncommon on the IGS, or indeed any In Character forum for any MMO, for someone to start a thread claiming X, Y, or Z about some faction's alleged misconduct without any evidence. Similar threads in this vein include topics that attribute certain attributes to certain in-game races or cultures based on 'empirical evidence' that is never presented because it of course does not exist, and furthermore has no canon backing.
The difference between these two sorts of claims is more than just politeness, it's effect. If you as a Caldari want to say that popped collars are all the rage in State fashion, then the only kind of people who will care are other Caldari RPers. They will consider your claim, and make the decision based on whether they think the Caldari liking popped collars would be interesting. However, if you as a Caldari want to claim that the Gallente like to sodomize chipmunks, then it becomes political.
Politics is a huge part of EVE, it is in fact the game's primary draw: Sure other games might have more involved combat or more varied environments, but in EVE more than perhaps any other MMORPG you can build an empire. Or, if you so choose, support one. And an unfortunate inevitability of politics is a very Us vs. Them mindset. This mindset means that when you say the Gallente like to sodomize chipmunks, it won't just be the Gallente RPers with an interest in it: It will be the Caldari and Amarr who have a vested interest in tarnishing the Gallente reputation, it will be the Minmatar who have a vested interest in defending their allies (And making the Amarr look stupid). What results is not a suggestion on how to expand the Gallente background, but an attack from one side to another.
But is this necessarily a bad thing? As I said, politics and factionalism in general is one of the game's core attractions. You could certainly argue that mudslinging for the sake of mudslinging is a part of the community's culture, and that there is no practical difference between using fiction made by CCP and fiction made by the players.
Personally, I'm against making things up to serve a purpose, particularly when there's already so many 'true' things to rant on about. I am also as a general rule against mudslinging, seeing as two sides repeating their incompatible dogma over and over again loses its appeal quickly. But I'm curious if there's anyone who would agree with the above argument, or who would have other arguments in favour of these politically motivated claims.