Sorry, I don't understand your last argument. There's a thing that you don't want to do, and you have a free choice whether to do it or not, but you're saying that you'd do it just because it's available? Surely that just means that you do want to do it, no?

Likewise, the pigs have the same choice. If they don't like the game, they can, e.g. face in the other direction so they don't have to see it (like I do in pubs that play sport on TV). (In fact, I'd be interested to see if any pigs do this.)

Besides, pigs are social animals, and there's plenty to do in that cage --- there are other pigs to interact with.