Believers deem atheists as untrustworthy as rapists

You really seem to be struggling badly to understand this. Moral reasoning is the justification one gives for the resolution to an ethical dilemma, or to the justification of a behavior. If you are writing a paper in which you say that one should behave in a certain way because that’s what Kohlberg says you should do, then yes, that would be a low level of reasoning.

I do hope as you leave that you finally understand the matter.