The militia itself makes (or not) the people accountable, versus the judicial system where the laws are heavily biased towards cops (qualified immunity for example).
Another community doing the same thing could end badly, but at least, there isn't a judiciary system in place, with a different caste, that favors one group over the other.
So, creating a militia doesn't guarantee accountability, but it gets rid of a system heavily in favor of cops not being held accountable, thus giving it a chance to hold everyone accountable.