As YouTube grows and becomes a launching ground for more entertainment careers there will be more stories like this. The Internet seems to bring out the worst in some people, including the content creators. YouTube is no exception. The conversation needs to be about how to educate potential perpetrators that this is wrong, that asking underage girls (or boys for that matter) for explicit material or providing them explicit material is sexual assault.
The victim-blaming that I have seen is disgusting and although parental involvement with online activities is necessary the girls in question are not at fault here. They were exploited by a man who has no interest in their well-being. Sure, you can argue that 18 is an arbitrary age for determining sexual autonomy when so many young people are engaged in sexual relationships there needs to be a line. 18 years is the best line we have and the ambiguity of sex is cleared up a little bit with that line.