Look, you're a Pirate. Navy comes and CDs you. Following the Pirate ID rules you can't open fire upon Navy player until he/she does it first. You know that while that Navy is CDing you, the reinforcement is coming for you, you want to open fire but you can't. If you open fire because that Navy kept disrupting you and the Navy reports you for violating an ID rule, how will you prove that the Navy was "spamming" CDs?
You can't shoot someone for CDing you once or twice, so logically you can't prove that the player CDed you 20-25 times if he says that he did it only 3-4 times.
P.S Well... would also like to have CD spamming=Engagement, but Admins explained it and I think they're totally right in this matter.