i think having someone reprisenting an instructor is a very good idea although i must say at our club which on a thursday we do have an instructor and on a monday we dont, we do tend to help each other out and talk about the moves, sometimes advice sometimes criticism and its all taken well, for instance my friend was doing Nikkyo on me and wasnt getting the twist right so i'm like
No no point my hand towards my forehead AAAAAAAAAAAAAAAAAAAGH...yeah thats it!
we help each other, some ppl may not be open to this i guess but when your a small club you kinda help each other to perfect technique n stuff
you could always confront them face to face and just ask "hey man what have i done?"
if he's offensive then what the hell is he doing learning Aikido then? show him to the nearest Karate club