Doug, I would be surprised if you get this error for ALL your items.
Here's why, lets say you have your Bank Account Number as display only when you're making a money transfer. If it's not protected you could use the inspector on the browser to change the account number and make the transfer to a different account. (Of course you would ideally have a validation to make sure this type of hack doesn't happen) Hopefully you get the idea.
So, how are you setting the values of these display items? Are you changing their values AFTER the page is loaded (with for example a Dynamic Action)?