As the reporter, i would just like to say that i could have coped with being blown up (not sure about Skipper, you'd have to ask him), but i really do not like it when someone knows they have someone else stuck in a situation where they are already going to profit from their death, and exploits it to get as much as they can, that strikes me as plain greed. And as far as i am concerned, you should have blown me up, if i were you i would have blown me up, the ore was easily re-minable, and credits are all re-earnable.
There isnt a precise rule you violated i dont think (though im not an Admin), but the Merc ID clearly states, right in the middle of the description "*Can not pirate". And what you did was not 'suggest a bribe be offered', in fact as well as the "Yes, i am extorting you" line, you also gave a "Give Crimson his five million NOW Bowex" line.
This is about as far from dropping a suggestion that you might be paid off as you could get.
In my opinion, greed, and blatant disregard for ID rules is not something that should be permitted to pass.
As for the difference, while i am not an admin, i would say that if the target offers you money, it is a bribe, if you demand money in return for not attacking the target (which you did), it is extortion, a.k.a piracy.
Oh and that contract does not mention anywhere you are allowed to extort the victim, only destroy them.