no its because you have liberated to many towns. if you liberate more than 2 towns after ardea, which is inevitable, then talking to an orc leader will turn all orc's hostile, and if you liberate another town beyond that then you have tipped the scales of the war by taking half of the orcs towns away from them--why on earth would they not want to kill you on site? you need to reload a game unfortunately, liberating towns or crushing resistance camps is not a good idea til later in the game unless you don't mind missing out on a lot of quests. completing the game is no problem though it just might be a bit harder. but hey if you hate orcs that much its realistic that you don't want to wait to liberate the towns.
on a side note there are sometime random slaves, orcs, rebels walking a path. they are unnamed but i accidentely killed them all(3) when they were fighting some beasts near the pass of varant. afterwords faring became hostile to me and when i went to the nearby rebel camp of nemora, a bunch of named orc mercenaries from faring were attacking the camp. i hadn't even liberated a town yet, but i guess my point is i had to reload a couple hours of time so be careful about attacking/killing random orcs. small rebels camps and orc camps out in the middle of nowhere don't seem to have an impact on your reputation if you kill them though and sometimes you actually can gain reputation with one faction and not lose any favor with another.