I agree that you can ask that the Tv be turned off (or the channel changed).
Also, if these are old friends, could you simply tell them what you've said here, and suggest that you meet up at a different time if they want to watch?
It might also be possible to move to a different seat so you couldn't see the screen, or so that you were at an angle and couldn't see it easily.
Could you have gone home? It sounds as though it was very casual, if they had the TV on even during dinner.
As they're old friends, would it have been possible for you to offer to help with clearing up after the meal, so you had an excuse to be out of the room?