Is like a cult or whatever, it twists them into thinking its right. Truly, ever disowning a child is wrong unless the parent-child relashenship is harmful in some way, then, even then, tge children should not be disowned, they should try to make thing better and if its not possible, than stop talking or avoid each other. I read a story about how a single mother was too dependant on one of her kids and all the rabanim and doctors told her the best thing would be to cut off contact for 10 YEARS! It was really sad, the story said so far 7 years have passed and she is still waiting out the rest.
Children even as they are adults need utmost love no matter what. Even if they go OTD or want to serve their country.