One tip the article suggests below is not rubbing your dog's head but instead scratching him underneath his chin. There are additional tips as well to help your pup become confident and fend off the bullies. It's important to keep him safe and help him overcome his shyness.

Just like a “wimpy kid” in middle school, you’ll know if your dog is getting bullied if, in social settings like the dog park, it gets frequently mounted, has food, water, toys, or spots stolen, gets ganged up on, or even gets badly injured. Its response to other dogs will often seem intimidated and defensive — even before any other dogs “act out.”

Dogs that get picked on “in public” may otherwise be happy and well-adjusted at home, but they may also display signs of being overly submissive.
If your dog displays overly submissive behaviors like rolling on its back or urinating in an interaction, it’s best to avoid eye contact, ignore your dog and walk away when such behaviors occur.

If your “wimpy kid” dog is otherwise content and confident at home and with people, it’s not a bad idea to get it some social training — either at an obedience school or with well-balanced, well-led dogs who can help it feel safe among peers.

Make sure, also, that your dog is mature and trained enough for the dog park environment. If you do go, you should remain alert and aware, showing your dog that you are still pack leader.

In the case of having a dog that gets picked on repeatedly by another one of your own pets, you might want to focus on disciplining and training the more aggressive pet.

Overall, by prioritizing your dog’s sense of safety, you can minimize its fearful tendencies and increase its sense of self-esteem and stability.

Remember one of the first steps to helping your pooch become confident, according to Cesar's Way, is surrounding him with safe dogs that will be kind to him. Obedience training will also help socialize him and hopefully over time he'll be great around other dogs. Be patient with him and help him feel safe during this process. Soon enough he'll be a confident Pug who doesn't have to deal with those doggy bullies!