ainatan said:
Exactly, that's why you don't need to get a free attack against a paralysed opponent, you just make a coup de grace and kill him.
A paralysed character, or an unconscious character can be considered to be out of combat, the same way he doesn't defend himself from you, you also don't need to be defending yourself from him, you both are not "exchanging blows, dodges and parries" anymore, so none of you can really lower your guard and provoke an AoO.
Also, a paralysed opponent is like a door, and if you are in combat and need to break down a door for any reason, you don't get a AoO against it just because it's not fighting back or defending itself.
Any others have pointed out, this counter argument lacks a lot of uumph.
If somebody wants to attack somebody who is paralyzed as a free action (an AOO), they should have the right to do that, minimally.
They can also, if they want to do a more serious attack, start a coup de grace.
The point is, AOO's are free, don't take actions. They should be allowed if you are paralyzed, since they are allowed when you are trying to stand up.
The other side of your argument involves flavor text which is not going to get very far.
A low-level unarmored unarmed wizard facing a dragon is hardly "exchanging blows, dodges and parries" with anyone. The person CAUSING the AOO to be created (like our wizard) does not need to be armed, in fact, can be a total wimp. In fact, if an unarmed wizard tried to hit a monster with his fist, that in itself would generate an AOO. Not only is the wizard not exchanging blows, he is making sure not to. The enemy, facing the wizard, is not parrying or dodging anything, since the wizard is not attacking.
Yet the Wizard generates an AOO for casting a spell next to the dragon.
It's the wizard's ACTION that is generating the AOO.
There is no "dance of death-dealing thrusts and blows" going on between the dragon and the wizard, and when the wizard pauses for a moment to cast a spell, the dragon cuts through the wizard's defense. No, the wizard is just standing there, NOT attacking, though presumably defending, and casts the spell, which... generates the AOO.
You stated: "Also, a paralysed opponent is like a door, and if you are in combat and need to break down a door for any reason, you don't get a AoO against it just because it's not fighting back or defending itself."
Your PC can be paralyzed and you can manifest a psionic power that generates an AOO (I think this is legal), and in this case the "door-like" PC, which is not fighting back or defending itself, gets hit. Yet the "door-like" PC which does not manifest a psionic power does not.
You can explain; I can't.