It is not the basic principle of d/f that is bad , but the way that it is applied. The movement has its rules , you break them continually, they can tell you to leave said movement. However should that stretch to shunning family members? That is a another add on of The Society.
In this case , even within WT rules , the elders had no right to tell them to kick out their son. The parents, should have told them it was a family matter and not their business
it reads like a case of stupid hard necked elders and weak minded parents.....