[header] How to stop a coworker putting down another coworker [title] Identify signs of bullying. [step] Whenever you hear a co-worker putting another co-worker down, stand up for them. Make it clear to the bully that you have your co-worker's back. 
Your co-worker's bully may back down if you call out their behavior. Still, remember that you are in a work environment, so be professional and polite.