If you read the BP pages that replaced the adult ads section, you will see that your question is directly on point.  

There are several docs posted by BP from reputable orgs known for aggressively fighting child trafficking and abuse who urged congress NOT to do this. They each cited how BP was in fact a key tool and organization in the fight to stop child trafficking. Like the RB and CL board actions earlier, this will end up accomplishing the exact opposite of it's intent.  

The law of unintended consequences rules the day.  And more trafficked and abused children will suffer.