What do I have to do to prove to you that unencrypted channels for Comcast cable are going away? You will need a cablecard of some sort of cablebox to watch channels.
Let the facts do it for you. Provide quotes of the relevant regulations and explanations for why it is being done. For example, explain that the cable companies want to ensure that everyone using their cable service is paying for it, even if they are watching a broadcast channel. The cable companies are making a lot of money and want to prevent "theft". For example Cablevision of New York City wants to use remote activation and deactivation to "reduce costs for Cablevision, improve customer service, and reduce fuel consumption and CO2 emissions" (I quoted that from the previously referenced FCC regulations). So now, if a cable company can remotely activate and deactivate a cable subscriber, the cable company can encrypt the signals, even for the basic (broadcast) channels.
You need to say something like that, except you probably should have a link in your reply to the FCC regulations.