Does the idea of grooming your dog cause you to tremble in fear because he likes to bite anyone who even thinks about brushing him or trimming his nails? Often, this difficulty starts off with a single bad experience. Maybe the person trying to brush him was being too rough and it hurt (creating that "hated" brush in your pup's mind). Maybe someone trimmed his nails too short and they bled. No matter the cause, things like this tend to stick in your pup's mind and make him afraid the next time.
Your dog probably learned to hate being groomed through a single incident such as those above. The mere idea of being groomed sends him into a state of fear and anxiety. He really isn't mad at you, he is mostly just scared and trying to tell you in the only way he knows how. The good news is that with a little time, effort, and patience, you can reach the point at which your pup will let you groom him while he patiently waits for you to make him look his best.
Bear in mind it can take a lot of hard work and patience to calm Captain Bite-tastic and get him to stop trying to chew your face off each time you go to brush him. But remember, you can make the entire event fun for both of you, and always have plenty of treats on hand.