Well, something I've noticed:
If you're an OT character talking to a random Clan character, and you're being "very Omni-ish" and confrontational... most of us, particularly those who don't actually know you, will just sigh, roll our eyes, and go back to what we were doing.
The people who do reply more than half-heartedly will be the ubah leet dewdz whose adolescence doesn't allow them to 'shrug it off' and therefore feel a need to refute anything that isn't a paen to their superiority.
And the reason is simple: From release until the Sentinels took over Tir, Omni players could safely grid in to Tir - and the Tir grid square was our biggest gathering place for finding teams, buffs, and trade skills. These Omnis often proceeded to spam in vicinity or on shout about how the Clans all suck. It wasn't uncommon; in fact it probably happened on a daily basis.
We ended up just being conditioned to tune it out.
Finally, Re: Greenies. I guess that's just life. The biggest "stealth nerf" in the game is that there's pretty much no "reason" - no advantage - to being Clan as opposed to being Omni. It continues to this date, whatever Kithrak might think about Clanners being the favored children of Funcom.
Just take a look at the Land Control map and reference it with the Grid exit and Whompa maps, and then try to tell me that Funcom favors the Clans.