One of the more difficult things to do, for many of us at least, is to react in the moment, when injustice is occurring right in front our eyes, but in a way that does not directly affect us. The "safe" thing to do is avoid the conflict, to get away and certainly not get involved. However, there are times when the safe thing to do is not the right thing to do.
When blackness is conditioned into the psyche of a society as inherently bad, there is no such thing as children -- only blackness and the "badness" that comes with it. It is this ideology that leads adult white men -- police officers -- to use the kind of force we've seen in the McKinney footage against black children.