It's right here, actually:
Which wouldn’t excuse his acting like an ass with a gun, of course (any more than it should excuse an officer doing likewise).
The Castile situation is very murky. A hypothesis that seems to me as likely as any, is that Philandro went head over heels for a mock-gansta lifestyle for the sake of his new girlfriend, who so worshiped him that she wanted him to have a funeral in a cathedral as a “king.”
The trouble came when play was treated as reality. It is one of those freak situations that, at least, I could not see an easy way to help from the officer end. The moral lesson would be that you affect evil for even dabbling reasons, it can come back to bite you. Which applies to a lot of situations, hence the newspaper’s nosing into the nature of the training — of course everybody understands the principle.
Anyhow, even the relatively righteous King Solomon could tell you about women temptation trouble.
And this shouldn’t be the cause for rioting in the streets, no. But for public transparency, yes.