Aren't the animals already dead when we purchase
meat in a grocery store?
Yes, the animals are already dead when we purchase meat in a
grocery store. However, this is only because we are, in effect,
hiring someone to kill them for us.
The number of animals which are bred and slaughtered depends directly on the consumer demand for meat. Every time we refrain from purchasing meat in a grocery store, we reduce this consumer demand, and ensure that fewer animals will be bred and forced to suffer.
So, although the animals we are eating are already dead when we purchase meat in a grocery store, doing so directly increases the number of animals which will have to suffer and die in the future.
Follow up questions:
Meat tastes too good to become a vegetarian.