Dragon is in charge of a real army, and these people are his subordinates, not his friends. The Revolutionary army have an agenda to achieve. There is no weakness to be shown here.
It's no different than the Marines who kill traitors, and punish those who commit treason.
Quit acting like the Revolutionary Army is supposed to be a tight knit crew, who treat each other like family just because most pirate crews do. They are not a Pirate crew. They're not his family. They are not his friends. They are there to do a job, as is he.