dialogue - Daniel Day Lewis Quote in Last of the Mohicans

In The Last of the Mohicans, Hawkeye, played by Daniel Day Lewis, appears out of the forest to save the Major from a raiding party of Indians. When the Major grabs a gun and is about to fire at one of the Indians who is running away from Chingachgook (Hawkeye's father), Hawkeye stops him and says

In case your aim's any better than your judgement

Shouldn't he have said

In case your aim's **not** any better than your judgement

I can't imagine the Major would intentionally shoot the people that saved his life.

Here is the action sequence:

The scene in question is about 2:50 in.

Answer

The problem here is that the major is aiming at Chingachgook. The major may think he's one of the attackers running away. It's clear that he's aiming at Chingachgook because even after Chingachgook kills the only other Indian within the line of site of the Major, the Major keeps taking aim.

Obviously HawkEye doesn't want Chingachgook shot, So since the Major's Judgement is that he should shoot Chingachgook, one of the guys who just saved him, his Judgement is considered by Hawkeye to be bad. If his aim is better he might actually hit Chingachgook