it's so wrong in my eyes

I was at work the other day and I must admit I was a bit shall we say angry at a customer.
The woman in question had three children, they were only young I would say the oldest one was about 9 years old.

She came to the counter and was asking my advice on games, She asked me about a game called Getaway. I said "it is a very violent game and deals with adult theme that's why it has a 18 rating, I would not recommend you get this game for them, in fact I would strongly recommend you don't!"

She said "is it worse than Grand theft auto?" I said " Yes I would say it is"
She then said that they play games like that all the time.
I could feel my self getting annoyed with her, what was she thinking?

I then said to her "This game is a 18 rated game which means it has violence and offensive language in it, it may also have sexual scenes in it also"
She gave me a look as if to say I don't really care.

by now the kids where pestering the lady and I could see her thinking I just want to get the game to keep them quiet.
I then said to her " I really think it would be unwise to get them this game, it would be like putting a 18 rated movie on and letting them watch it"

after all my pleading with the customer not to subject the kids to the game, she said "oh I'll get it for them, if they start swearing I'll just turn down the volume"

I said "but its visual also"
She said, "oh they will be fine they have seen worse"

there was nothing I could really do, I had to sell her the game but believe me I wanted so badly to refuse her.

and as she was leaving the store she turned to me and said "I am not a bad mother"

I don't think she was a bad mother, her kids seemed to love her. I just think that it's not right that there is no law saying you can't buy a game/ movie that's a 18 for someone younger than that age.