Get rid of "animal man/woman" corpses

Animal-men have the [CAN_LEARN] tag. This means they are sapient creatures and dwarfs cannot butcher or eat them. To get rid of them, leave them in a corpse stockpile until they rot into bones. You can still use their bones for crafts/bolts/etc.

If you want to remove them altogether, you could delete them from the raws. Go to the folder where Dwarf Fortress is and go to raw/objects. Most of the animal men are in creature_subteranean. Either remove the [CAN_LEARN] tag so you can butcher them or remove the entry altogether.

Note that you may have to start a new region for these changes to take effect. Backup any files before you change them.

As the man/woman part of the creature name mentions, those beings are at least borderline sentient and can therefore not be butchered for meat. Your best bet is putting up a corpse stockpile and letting the bodies rot away naturally over time, or set up one of several garbage destruction mechanisms (magma pit garbage dump, dwarven atom smasher, etc)