If your camera mic is mono, ignore the rest of this post....
One thing that is a very long shot would be a "reverse" karaoke effect. This normally analyses music, and filters out the "mono" component. With most pop music, the main vocal will be central, while the instruments will have a stereo spread. So a karaoke effect will remove the singer. A reverse karaoke will remove the band.
If your TV sound is somewhere off mike, and the voices are nice and central, it may have enough stereo information to allow a plug-in to distinguish between the sources. Studio 9 does have a karaoke effect, but you can't reverse it. You could use it to test the idea, though
I couldn't find a free one that would reverse, but there is a VST plug-in on offer HERE thet you might want to consider.
ADDED reading about the plug-in, the demo works but you can't make fine adjustments, so it's worth a download.