You're forgetting they didn't attack you to be the big bad meany trying to take candy from a baby. They had a reason for attacking Rindyar, but you can ignore that and pretend you're the helpless child being harassed for your candy.
I don't think you quite understand that the only faction with a halfway legitimate casus belli (reason for war) happened to be Hero Party, who had a claim on New Rindyar. While it is legitimate, it is also disputable as the owner of the fief was not in the HP Strategus Faction and gave the castle away to FCC following a raid (which was followed by negotiations). The owner of the castle could have kept the castle and waited for reinforcements from HP, yet they instead decided to cede the lands to the Companies. FCC then sold the fief to Frisia, who was at the time forging an alliance with NH.
So, Hero Party decided to strike and take back their lands, they sent approximately 2,700 troops followed by some thousand Occitan troops. Hero Party's force, lead by Shik, turned around and headed to go raid a fief in the distant edge of FCC's border. Occitan used what could be called an alliance casus belli (for you EU3 players) and marched in instead to grab the castle for Hero Party, which was already using a faulty, disputable, reason for war.
The drama that followed was mostly just Fimbulvetr and friends calling out HP and Occitan for being the massive hypocrites that they are as they attacked a small 10 man faction under the pretense that it was, indeed, a small ten man faction. Once they discovered that it was not as small as they had previously guessed and that they indeed had allies, they began to bitch about being outnumbered, being the under dogs, and of course this only got worse when VE jumped in for a land grab.
The point I'm trying to make is that Hero Party and Occitan's reason for attacking Frisia is arguable and is without solid backing. Although it'd be nice to see everyone quit this "NO WE R TEH TROO UNDRDOGZ!!#11!!1!" bullshit.