Personally, I would much rather pay a slightly higher fee to insure we do what's right than to keep polluting and not worry about the damage it causes not only to the environment, but to the people who live and work in the area. It's companies like this that care more about their bottom line than to the ecological damage they cause. It speaks volumes about them when they choose this path instead of taking the path other cruise lines have taken to insure they meet or exceed local environmental protection laws.
If they decide not to abide by the laws, then hopefully others will fill the void who want to take on the responsibility to do the right thing.
And if Cunard decided to leave New York, you're right - it would be amusing!