This is just the Bayesian approach; overall men have high enough tendancy for aggression and sexual assault that from a risk analysis point it makes sense to be on your guard until you get to know that person better. Of course media has a bias for presenting the awful stuff that happens in the world, one would rarely get coverage of a heart warming relationship between two people involving atleast one man. So these priors despite being in the correct direction might be biased too.

But I think, neither the shark anology or the expression "all man are dangerous" is useful for getting this point across though.