Eating flesh of dead bodies is definitely poisonous. That is exactly what happens to those who practice gossip, spying and backbiting. They do not only assassinate dignity and reputation of others, but also poison purity and innocence of their own hearts. The damage they cause to their own selves is bigger than the damage caused to their victims.
O you who believe! Avoid much suspicion; indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting). And fear Allah. Verily, Allah is the One Who forgives and accepts repentance, Most Merciful. (49-12)