Yeah, HDCP (high-definition copy protection) makes an attempt to make content viewable, but not copyable, but it only works by certifying every single piece of the chain and it's still vulnerable to someone using a simple video camera to capture images of the displayed message.

Barring a human-computer interface that conveys messages directly into someone's brain, I don't see this as possible. If you can see it or if you can hear it, then it is copy-able.