Why does the doctor threaten Mr Hand first?

Dr. Livesey then warned Hands:

“Mr. Hands,” he said, “here are two of us with a brace of pistols each. If any one of you six make a signal of any description, that man's dead.”

Mr. Hands is kept at bay by Livesey's threats. This shows that the mutineers are cowardly individuals. They only seem courageous in big groups.