Not Tainted

So i was watching a DVD with my niece and nephew. We were watching Family Guy the movie. Now the rating said parental discretion advised, but they alluded me to the fact that their parents let them watch it before. My niece and nephew are 7 and 10. Personally I have not watched much of Family Guy, but from what i know its not a family show. So they convince me that their parents wouldn't mind. In the opening minutes of the movie their were some cuss`n and I was about to look for the stop button as they laughed and giggled. I let it play and little longer and found it funny but still not appropriate for them. I labeled this not tainted with a smile and thank you Lord.
The skit in question:
So the baby (stewie) in the movie was in the bathroom shaving his testicles and the dog barges into the bathroom. Stewie asks the dog to shave his coin bag and the dog respectfully declines. So this reminds Stewie that his coin bag could be the twin brother of some TV show guy he watches. {at this point I'm like this is to much and they can't continue to watch this cartoon and I don't care if their parents have let them seen it before} The movie goes into in episode of the coin bag look-a-like in a matching chaps and hat as the TV show guy. So my niece says to her brother, and I quote"you know that's his butt right" and my nephew says some remark in the lines of "of course I know that". I smile and thank the Lord that they have not been tainted and are still children. Children are exposed to so much these days and I always wonder how much do they take in and understand.