He's stating that the evidence is P(Was Relative | Child Attacked) is relatively high, especially compared to P(Was Total Stranger | Child Attacked). This means that it should, if you use Bayes' Theorem correctly in everyday life, shift your suspicion away from the random photographer.

Of course, since P(Child Attacked) is so very low it's still not a huge deal.

It's not really backwards. That sort of inversion is exactly part of Bayes' Theorem.