Yeh toh Shubh ka balha ho ke he realized long before otherwise I dont think anyone wud find their way right by being left alone without the right guidance.
Shubh knws the difference btwn wrong n right n that is not the point. All he needs is a little understanding n support. They cud have heard him out, n tried understanding but one after the other his ppl jus pushed him away.
If Parikshit believes that by going with Shubh they wud have shown he is right then by living with Karthik they r showing he is right. If kids must b left alone to realise their mistake n repent then Par-Gayu shud have left Karthik at first cus no matter wat Shubh has done he has never insulted their thoughts n beliefs like Karthik has many times.