This is a fallacy, called generalization, when you take a part of the group and based on his attributes you make a statement about the group as a whole, but is persuading to Reason, because it makes sense that if he is an nonourable man, he would be in the company of other honourable men.
I believe that the persuasive appeal of (C) Reason is being used here. It implies that since Brutus is an honorable, then by that all logic, all men must be honorable.
