The solution is to play your DVD on something other than a Blu-ray player. The only way the Cinavia message shows up is if you are using a hardware player that has Cinavia detection, or a software player licensed by the Blu-ray Association.
Many Blu-ray players that have Cinavia detection will not mute the audio and display the warning if you play the video from a USB stick. So if you insist on using this player, try ripping the DVD to an MKV or MP4 file and play it via the USB slot.
If that doesn't work, buy a Roku or WD TV Live, or one of the many other streaming media boxes and get used to playing content that has been ripped from your optical discs to MP4 or MKV files.