Interesting question! Parents are most certainly responsible for instilling morality, but oftentimes, TV and Music Videos do.
Teaching morality starts as an infant -- is greatly impacted during the toddler stage and continues with every interactionwe have with our children. Parents who regard all interactions with their children as teaching moments, have children who have great morals -- waiting to teach after the fact (or a moral indescretion) will watch their children make poor moral decisions for years.
Morality, like anything else, is taught and learned.
When all children see are the morals that are shown on TV or in music videos, that's how they behave, morally and otherwise.
There is a great deal of research done in the Morality field. You can easity research morals, how morals are taught or learned and why people either accept or go against morals.
I hope this helps.