I don't understand how torturing animals is a fun way to celebrate a festival, such as dog eating festivals. It happens not only in Vietnam, but all over the world.
There are Catholic festivals in South America torturing animals, there are festivals in Nepal that torture animals, there are festivals in India......it seems that animal cruelty is considered part of the fun all around the world.
On a very small scale, consider children catching insects and pulling off their legs and wings, while parents look on and smile at the fun the kids are having......
Kim