I feel like no matter what animal people use to insult a human, the human is usually worse than the actual animal. Even with snakes. Muskrats are sweethearts, they just swim around ponds and tag along with beavers.
Snakes, rats, sharks, and pigs. These are all beautiful animals, but describe terrible humans. These animals don't deserve the association. I agree with you, and maybe we should stick to double-crossers, snitches, shysters, and cops or find other catchy names that work.