Hello. A colleague and I discussed the possible reason for youth delinquency. And he mentioned it resulted from the proliferation of Women in the labor force. I felt so angry about his explanation! Is anyone could help me to “fight back”?

Welcome!

Wow. Thank you so much!

Yes. your colleague's arguments indeed sound unpleasant. Yet, many scholars also admit that adult supervision is significantly affecting youth's behavior. As a fact, women, both in Western and Chinese, have rapidly increased their rate of participation in the labor force over the past 40 years. As indicated by the 2012 Current Population Survey in the U.S., 76 percent of women with school-age children are in the labor force presenting the need for families to find care for their children during non-school work hours. Research has linked leaving youth unsupervised in the after-school hours to negative behaviors. Using data from the 1998 wave of the National Longitudinal Survey of Youth, Aizer (2004) found that children without adult supervision were more likely to skip school, use alcohol or marijuana, steal, or hurt someone. A 2006 survey of over 600 youth age 12-17 in California found that kids left unsupervised three or more days per week were twice as likely to hang out with gang members, three times as likely to engage in criminal behavior, and over three times as likely to use illegal drugs (Fight Crime: Invest in Kids, 2007).

You could find more information with these references:
Aizer, A. (2004). Home alone: supervision after school and child behavior. Journal of Public Economics, 88(9), 1835-1848.
Fight Crime: Invest in Kids. (2009). Factsheet: After-school programs prevent crime. Washington, DC: Author.

However, we shouldn't blame mothers/women for this situation. It is also the fathers' responsibility to take care of children and the family. Hence, we should act to cope with the transition of modern families.