If that’s your opinion of him, why did you let him into the group? Or did you not feel that way about him until he was in the group, in which case, what actions of his do you even disagree with? Because you seem pretty in sync with him about willingness to kill, while the Makarov thinf is the only real foolhardy thing about him right now. Otherwise, if it’s the stuff he did before joining the group that you object to, then… don’t let him into the group, and he won’t be able to affect it?
That’s all aside from the point that murder as punishment for possible risk is brutality, plain and simple.