Sad fact. What many keep as pets is a delicacy to others. In a way, I suppose it's no different to chickens or sheep, some people keep them as pets and others farm them. But I couldn't imagine keeping guinea pigs to eat either When I go to other countries and see delicacies like that, I often think 'thank God I'm vegetarian!'

BTW, if you type 'guinea pig' into Google Image Search, one of the first images you get is a picture of roast guinea pig