Unfortunately it doesn't seem there is a rule to protect against CD spamming, and under 5 is usually enough to have great effect on a situation. Ironically CD'ing you made the Freelancer's potential services useless, why pay when you're already getting away for free? I'd say in that case there should have been confirmation from the trader first, seems like someone jumped the gun and then went away happy they at least messed with someone else. Way I see it is a FL gives a service to a trader, it shouldn't be for free, and demanding/asking for payment after the fact seems like the wrong order. If the trader didn't offer something for help in defense or getting away, it seems like something went wrong there. It may not have been an engagement outside of ID rules, but in a way it was the giving of a mercenary service prior to any confirmation or agreement that make a contract. I would like to finally see some clarification in the rules about CD spam, maybe something should be changed to cover ID's that don't allow for making demands like miner or freelancer. That would make it so generics couldn't be used for trolling. Freelancers firing CD's after contracts are established would be no problem. Basically any CD should sort of be accompanied by either a demand (to stop) or straight up engagement notice. Until you have reason for either, you don't really have a reason as a FL to use your CD against another player.
What he should have said was 'hey i'll cruise disrupt that pirate for a million credits' and even if the trader had said 'ya', he would have got what he needed for there to be no question. What the pirate then does about that...is a whole other story.