Argh whats the fucking point in some IDIOT coming in and killing me when I am fighting a fucking big bunch of guards?! PS3 > Set offline.
Stupid.
lol. I agree it is really frustrating to get invaded sometimes by people who attack you as you're fighting the AI. I prefer if they try to do a cat and mouse game, using the AI to their advantage but not attacking as soon as they invade if they see me fighting AI. Not everyone is an asshole in this regard, and as a phantom luring players into AI aggro range can be a good strategy.
Unfortunately turning human is sometimes more of a hindrance than a help. The situation you described.. that's the risk you run walking around as human. But again not everyone acts that way and I think you're missing out if you set your PS3 offline!