How come vietnamese youngsters like my nephew don't get what their elders are saying through their heads?

My bi polaric nephew is going out of control later this week and his mom is about to lose her job because of him. He constantly calls in his mother's work place when he is feeling depressed and wants to whine and ask her to help him and now the employer is extremely mad and confronted him about his excessive calling. He would always call in there and whine to his mom on the phone about why is his life so hard and why he can't marry that girl from vietnam that she promised him that he can marry. He cussed the employer out on the phone when she confronted him about his excessive calling and was screaming to the employer on the phone. The employer is thinking of firing his mom because of him. He keeps on throwing fits saying why can't he marry the girl from vietnam. We tell him in order to do that he must have a job but he just doesn't get it and continues to throw fits. He told me on the phone that he will kill anybody who gets in his way of him marrying the vietnamese girl from vietnam, he said he would kill even the people in vietnam who gets in his way. He is going out of control and we can't stand him anymore. I think he is going to be in big trouble if he ever goes to vietnam. Almost everyone in San Jose can't stand him so people in vietnam can't stand him either I believe. I've about had it with my nephew. He was acting very mature earlier in the week and now he is like totally a different person. This pattern repeats itself each week. He would have 3 days where is fine and about 4 to 5 days where he would be grumpy and mean and out of control. How come he just doesn't get what older people tell him ? I've noticed a lot of young vietnamese folks now a days has some sort attitude like he has. He always has an attitude with me when he talks to me.