A dog's behavior may have many reasons, and it does not necessarily mean that he is mean to men. Dogs may exhibit different behaviors due to their environment, experiences, training methods, or other factors. Sometimes, dogs will be aggressive toward men because they feel fearful or threatened. For example, a dog may become defensive about men if it has been exposed to violence or has seen men being violent to other animals.
Dogs may also be wary of strangers, including men, because they have not received enough socialization training. In addition, dog breeds and individual differences may also affect their behavior. Some breeds are naturally more protective of their owners and may be more aggressive towards strangers (including men). If your dog exhibits aggressive behavior, it is recommended that you seek help from a professional animal behavior expert. They can help you understand the reasons behind your dog's behavior and suggest appropriate solutions.