Nobody's saying that it can't be real because girls don't grok tech and 16-year-olds are stupid. They're saying it's unlikely to be realy because statistically, the number of 16-year-old girl hackers is very small (relative to 25-year-old male hackers), there's a huge history of fake personas in hacking (and especially around Anonymous), and a 16-year-old girl is a very useful persona to get attention.