Clothes are a type of nonverbal communication, like you said...it is what it is.
I don't think Raggs means to imply a person needs to wear a suit when OCing. I think what he's saying is that when you go into public acting as a representative of a group, even informally, paying attention to the way one clothes themselves deserves some consideration. Am I saying that a person shouldn't OC in shorts and T-shirt when going about their daily activities? Not at all. What I think prudent, though, is when a person represents the larger OC community, one should attempt to dress as well as, or slightly better than, the general public also present. A collared shirt, although not absolutely necessary, would have probably been more appropriate for that person to wear.