Hi Crunchsite and welcome to Cruise-Chat.
It sounds like you had a very frustrating last day on the ship, between waiting on line and being on the phone, with no resolution to your problem.
I agree with those who suggested writing them a letter with the appropriate documentation. Your travel agent is your advocate as well, and can follow up with phone calls to his or her contacts at the Princess offices. I hope you used a travel agent to book this cruise.
It's unusual to see someone negate his whole cruise experience because of a frustrating incident, as well as painting the whole cruise line with the same frustration-laden brush. Princess is a very successful and popular cruise line, a status it couldn't have achieved and upheld if they were really "thieves." I'm sure you've made a mistake or two in your life, and know that honest mistakes are made and rectified. Perhaps what you heard as rudeness was their frustration at not being able to help you further at that particular time, because of a lack of documentation, or whatever.
In any case, I doubt you'll change anyone's mind about Princess with your message. Each of us gets to vote with our feet, and you're right that you always have the option of trying another cruise line in the future. In the meantime, I hope you get a resolution to your situation in a timely fashion.