Lets go with some scenarios.
The bard walks in and slaps the barmaid on the posterior. This offends the inkeep. Depending on the inkeeper's final reaction:
Hostile: Attacks the guy, throws him out of the inn.
Unfriendly: Gives bad service, raises prices, and acts surly
Neutral: Grumbles about it a bit, but doesn't take any action
Friendly: Explains to the bard about sensibilities around these here parts, and how his actions could be misunderstood.
Helpful: As friendly, but also smooths it over with the barmaid.
That's a fairly easy one. How about
Fanatical henchman of an evildoer, who's about to destroy the city
Hostile: Does his best to make sure the heroes stay in the city. If free, will probably lash out, attack them, tie them up or outright kill them.
Unfriendly: Does his best to make sure the heroes stay in the city, most likely by minor subterfuge. Unlikely to attack them unless they ask for it.
Neutral: Couldn't care less whether the heroes get killed by the destruction of the city. Will still not let them stop his master's plan.
Friendly: "Hey buddy, I was just going over to haverbrook today - wanna come? It'll be great!" - on the day of the destruction of the city.
Helpful:"Look, I can't tell you what's going on, but you have to leave the city for your own good. I really mean it. And you'd best watch your backs".
Note the evil henchman doesn't stop being an evil henchman just because he wants to help the heroes. The henchman can have MULTIPLE helpful attitudes towards different parties. Hell - he may even have different attitudes towards members of the same party.
And of course - if there's a fight going on, and the reasons for that fight are still present after the diplomacy check, then the fight will most likely resume.
ie:
Some orcs are fighting to defend their home. They attacked without warning.
Final reaction:
Hostile - duh. They still attack. Only they're not going to take prisoners, or tie you up and dump you in the forest as a warning to others. They want you dead. They'll coup-de-grace anyone who isn't already on -10 at the end of the fight. Surrender will not be an option for you. If you run, they'll probably pursue without a good reason not to.
Unfriendly - they may possibly make clear the reasons for their attack while fighting "You leave now, we not squish you!". Party members are left alone once they're unconscious, or dragged away from the area. They'll most likely be robbed. Surrender is probably an option, but you won't get to keep your stuff, and you'll be bound and probably beaten a bit. If you run, they'll probably let you.
Neutral - Sorry, but the fight's still on unless you quit first. Surrender will probably be allowed, and you'll probably be told to leave immediately. They may deal with you if your offer is particularly generous and your request minor.
Friendly - They're willing to stop fighting if you do. It was all a big mistake. You still can't come in, but they'll be willing to talk before you leave. You can probably make a fair deal to get what you want.
Helpful - As friendly, but they'll probably invite you in for dinner. You're probably welcome to drop by later.
Note that the orcs still have an agenda even when they're neutral and friendly - they wanted you off their land, and they still do. You didn't change that. They might be willing to bend in exchange for something.