The simplest way to think of the id is to hang around a toddler in the concept stage that is after "possession" but before "empathy." It's the stage where they go around grabbing everything they want and yelling "Mine! Mine!"
Life is never that simple again.
Unfortunately, some people stay that simple. Some of them become criminally violent, as in this study: CJO - Abstract: The present results suggest that violent offenders show dual impairments in inhibitory cognitive control. First, they are deficient in shifting attention from one category to another. Secondly, the ability to alter behaviour in response to fluctuations in the emotional significance of stimuli is compromised. These deficits might constitute cognitive reflections of the biological prefrontal alterations observed in this group of people.
Nutshelling it, the study found that, because of prefrontal lobe deficiencies, this group could not move out of a groove very well. Once the idea of "I'm going to punch somebody" appeared in their heads, its expression was well-nigh inevitable. In addition, all new ideas would appear in the same emotional framework. Once "belligerence" became the default operating mode, it would be expressed regardless of circumstance, be they the orginal annoyance, police officers, or Mom with an apple pie.
These people are worst-case, but there are lesser degrees of the same syndrome walking among us. It's expected in a toddler. It's disastrous in an adult. Because these people are only adult in body. Their mind has not progressed past a basic id stage. Their mind cannot process reality.
Don't mistake the adult body for the adult mind. So many times we are baffled by people's behavior because it does not make sense... and that's because it does not. We have to change our own frames to realize we are not dealing with another adult. We are dealing with someone who is stubborn, angry, and hurtful because they are out of their depth. They are constantly expected to act in an adult way, and they are incapable of doing so.
That's the reality, and we must act accordingly.