Well obviously the guy was an expert cyclist. He was after all.... riding a bicycle.

It may also have been a beginners club ride and a ride leader was offering advice to someone he mistook as a ride participant. OR... since that was/is the OP's club (and he hasn't been riding with them for some time)... the guy that yelled at him may have been a former cycling friend/club rider that the OP didn't recognize. The OP may have just been getting a good hearted ribbing from forgotten friend.