Shunning is emotional blackmail. There is no other way around it. It is not scriptural. Men have twisted scripture to make a system to control others. Would a God of love really intend to introduce this much misery into the lives people? This one teaching alone convinces me that jw's are not God's voice to humanity. Unfortunately, for those of us who are born in or long time members, the trap has been set and it is not an easy thing to extricate oneself. I have a wife and 16 year old daughter. My wife struggles with the idea that this is not the "TRUTH". My daughter has flat out rejected the cult. My wife and I can see that she is blossoming as a normal young woman with her caring friends who give her unconditional love and support.
Your father may one day come to the realization that he is in a mind controlled cult. In the meantime, live your life as best you can. Try to avoid bitterness that will not help you or your trapped family. A happy life, well lived, is the best way to combat the abusive behaviour of this mind numbing, manmade system of control.