From my experience there are 2 ways of dealing with people going too hard in training.
1 - go as hard as them, which inevitably turns into a brawl and nobody learns anything.
2 - ask them to turn the power down a few notches. If they refuse, then walk away. People like that are no use sparring with when you are just starting out.
Raise your concerns with your coach. If he doesn't address them then find a new gym.