I have often wondered this myself. We all get angry but most of us don't take action in it.

IMO It starts with the emotion of a given situation. If you don't have the ability to control the emotion and allow it to magnify to the point you take action on it the next step is the ability to do so. This is why controls are needed.

Trump is a great example of emotion run wild and impulsive actions and why so many think it is a very bad idea for him to have access to nuclear codes.

Should one of the controls be a self-control test?

(Trump should fall in a hole.)

In a political sense, not many "liberal" folks would own up in mixed company to conformity; creativity and artistic abilities would be on the block. Yet the two-way mirror may equate conformity with civility in the social order.

I think "liberal" mindedness has created cultural norms which assuage our misgivings about civility and conformity. It's OK to go topless at Eeyore's Birthday, but not to yell the "N" word on a public sidewalk. The more developed these cultural norms, the more diversions or tolerance when faced with a social control problem. In fact, these created cultural norms and mores can be its own mark of strength, as opposed to the more violent or macho tendencies we believe characterize "conservative" types.

Some of these in response to the mistreatment of others or of minority groups and some in response to others lack of a response.

Here on DU some jury alerts demonstrate a level of derision toward another that include an accusation questioning the roots, motives and allegiance of well known and long established members. Disparagement is acceptable for those who espouse non-comforting ideas.

OTOH there are examples of extraordinary sympathy and many folks real efforts to help those around them.
For example: http://www.democraticunderground.com/1018887672

In the Sapir–Whorf hypothesis it is postulated that one's command of language (or lack thereof) has an effect on his perception of the world around him. The very information of the signs of madness and detachment from reality have become both more accepted and less familiar to us all. Is Hamlet still a mandatory study in this age revisions in teaching theory? In his vacillation over revenge, six others are die.

If we accept that the actions of others in the world around us can influence our own levels of aggression, hostility and violence, can we justify a 'self-control test' to determine things about an individual's psychological make up that are predictive of aspects of an innate killer instinct, self-harm and social normality?

If we answer yes for those seeking to acquire weapons, shouldn't we answer yes for everyone? We have far more suicides than murders and since all deaths are a loss, should everyone be examined for these problems and deficiencies?

presume to wield power, even in the name of keeping everyone safe.