Compare....

And contrast...

One of these things sparked an "in-depth" investigation by a British national television station, filled with outrage. The other was a nationally released film widely regarded by the media as "just a bit of fun".
Can you guess which one caused the outrage? Yes, of course - it was the one without real people pictured in it.
Of course, the big difference is that, in Second Life and other online scenarios, the people doing the typing (and that is all it amounts to) are adults, talking to other adults, some of whom pretend to be under age.
In the film, you have adults, pretending to be young people who look underage but - it's made quite clear - are just far enough over the age of consent to stop you feeling like a paedophile. The fact that they look like they're underage - but aren't - is what "excuses" you, what makes it OK to lust after them.
The fact they look young enough to be attractive to exactly the same sexual predators as supposedly inhabit Second Life isn't an issue for the mainstream media, which happily accepts the advertising money for the film and reviews it as "a bit of fun". The fact that these are sexualised images of teenagers doesn't bother the media. What matters is that this form of sexualisation is traditional (and therefore OK).