Yes, I do understand your point. My background is heavily oriented in athletic training and rehabilitation. I do not have an M.D. if this is what you are referring to, however I have much practical experience and anatomical knowledge when dealing with these injuries. I myself have had a separated acromioclavicular and recovered quickly and to 100%. This said please understand that the advice i'm giving here is without direct knowledge of the exact injury. It would be a much more direct reference if I had this gentlemen in-front of me, this way I could first hand see the extent of his injuries. Again, be very cautious. Do not do things that could potentially cause the joint to fall out of place. An injury to the AC means that joint is VERY susceptible to displacement or further damage to the ligaments. However, these simple rotator exercises can be done in a controlled, low impact manner. This will be the only way to keep mobility and strength within the joint during it's recovering period. Also, the strengthened musculature will help prevent further damage to the ligaments by providing support to the joint during every day life.