"internet hate mobs" are the people that oppose this pretty douchey teacher?
There is almost always far more to stories like this than the reporting has us to believe. That's because the reporting is pushing an agenda. Which internet hate mobs etc absolutely love.
Not sure he really should have called the police, but it's up to him isn't it. But as I said, there's very likely far more to the story than just a blog.
If for example the story was "teacher calls police after student damages property / makes threats / brings knife to school / etc etc, and also shows police his weird ranty blog", then it wouldn't fit with the 'internet hate mob' agenda.