Being the gentleman that I am I can tell you that on the few occasions this situation has occurred in my Aikido career I initially used to fight fire with fire.If the guy wanted a war he got one.After a while I got fed up with this and later when it happened again[I a guy was throwing me in a break arm shiho nage] I had a quiet word in his ear indicating if he did it again I would do him.He responded favourably and we parted with a new understanding of the rules of engagement.Another occasion I recall was a violent confrontation with a young Japanese guy.Nearly feather dusters at hundred yards.We were separated by Fujita Sensei, the class teacher at the time.
Rather than get caught up in a death match , move away and just ignore the guy.If he comes back, you know he is looking for trouble.At that point make a decision.
Good luck , Joe.
If the guy keeps trying to coach you , just let him know you can work it out yourself No need for you to start getting uptight.Both of you getting aggressive wont help. Joe.