I mean, if I were a warrior and saw a complete stranger running towards me, katana in hand, I would think "whatever, let's just kill him and get it over with", but if I saw my sworn enemy doing the same, I'd probably feel really angry at him, and at the same time excited about the incoming fight, so I would put a lot more effort in the fight, right? And if, say, I start attacking a friendly faction, they would be shocked that I'm attacking them, probably begging me to stop and try to make me reason...
So, if a faction sees someone who they have a neutral kind of approval (e.g.: more than -20 to less than +20), they would normally fight if provoked
BUT!
if the one attacking them was a deeply trusted friend or a despised enemy they should be fighting with less and more strength respectively!
Let me know what you think, I'm used to be insulted