A 'badvocate' is a person who always proposes or supports doing bad things.
Good Guy: Hey gang, after we finish helping out these fine senior citizens, let's all go down to the malt shop and have some ice cream. My treat!
Badvocate: Orrrrrrr....we could light a box of kittens on fire!
Good Guy: You're pretty creepy always playing the 'badvocate'.