Though I have no idea what the context is in the original image, I would have to contest that any human being of unknown intent can be considered dangerous.

Unbelievable damage can be inflicted from one person on another with things as simple as keys or a pen, bare hands if done correctly.

Take for instance the Rodney King case, He was speeding and then took police on a wild chase, he admitted he did not pull over because he did not want a DUI because he had previous robbery convictions and it would violate his parole.

He was shot with a taser two times and still tried to fight...

Now I do not condone excessively beating the man while down, however if you had been one of the officers would you have considered the fact some real force was justifiable, I certainly would have.

In the end, most often an officer has to potentially jeopardize his life to prevent people from doing stupid things to themselves or one another, and considering that looks like riot control, they do it in significantly out numbered odds.

Big cans of pepper spray change those odds to slightly more equal.

It is likely the man was asked to leave multiple times, refused to do so and the spray was deemed less forcible than a baton.