I remember swearing at my Dad aged 5 (think I called him a sh*t head as I'd heard the phrase said on TV). He leapt up from his chair, chased me around the house and washed my mouth out with soap and water. I never swore at him again (well, not in my childhood or teenage years...).
I'm a strong believer in upbringing as an influence on later life and behaviour. I'd love to see how these delinquents were raised.