Why does enabling CEC on my HDTV prevent 7.1 Dolby Surround from working?

Episode 1454 (2:03:02)

Don from Arizona
Vizio 70" HDTV

Don has Vizio 70" HDTV running through a Sony 7.1 surround sound system, but when he enables the CEC functionality, it takes away the 7.1 Dolby surround. Leo says that CEC lets him turn on the Apple TV and lets it control the receiver. The problem is, results vary from TV to TV, so one TV may give him the center channel while the next doesn't. Leo advises turning off CEC and let the receiver handle it. It's more likely that the device isn't encoding it properly.