Are parents to be credited &/or blamed for their adult children's general behavior?

After Kanye West acted out at the VMA’s by stealing the mic from Taylor Swift & insinuating that Beyonce’ deserved the award instead, I said to myself “that kid’s mother should have taught him better than that & instead she raised a punk”.

My friend (both a single mother & the product of one) began to take up for Kanye’s mother saying that we raise children up in the way we want them to be but they don’t always go in that direction once on their own.

It is my point of view that regardless the race, gender, religion, economic status, life experience etc. of a person if their parents taught them correctly then they will know the time & place to say/do certain things & not be publicly disrespectful of others in general. What does fluther think?