There's the famous image from quite some years ago of a UK Police BO-105 being used to move protesters in a field by flying at about head height and used in the same way helicopters are used in Oz for cattle herding. Unfortunately I can't find a copy online.
If just one of the protesters had been injured, or used a rock to defend themselves the story would have been very different. If someone sees an agent of the state trying to stop them protest, sure as eggs is eggs it'll turn nasty at some point. And the damage averted by a fallen tree branch would be multiplied many times if an aircraft came down, and it would be cold comfort to blame that on the protesters.
Similarly with the swimming escapee. While I'm sure a rapid risk assessment was done at the time, had he drowned then there would have been some awkward questions asked I'm sure.