Insecurities is a huge reason that people react the way they do.
Most times we react because of what may have happened to us in the past. In your growing up years you may have been laughed at or overlooked, beat up or ignored. It all becomes our make up, our DNA if you would.
As we grow older we think we outgrow things or brush them away but they seem to always bubble up. People get defensive or angry where at times you would think it should be such a big deal, but they are actually reacting to something else, something in their past.
People become insecure because of fear also- fear that they may lose their job or fear that someone may get work that they think they deserve..all things really out their control for the most part.
What happens is they make their fears come true when they act on their insecurities rather then just doing their job and blocking the rest out.
Insecurity grows out of not preparing properly too, not doing your homework and accepting responsibility. When something goes wrong they are quick to point the finger and yell. It is a huge smoke screen that says - hey, don't look at me. They know deep down that they could have help prevent the situation so they try to deflect .
What happens too is through insecurities if and when people know that they may be at fault they then try to turn others to their point of view, assuming their is comfort in a crowd. The funny thing is the people that they are trying to win over with their argument probably do not even care. So they fan the flames and agree and egg them on.
Being insecure is deep rooted and can hurt and hold you back.
There is no easy answer- just try to think back on situations as they occur and ask yourself- just how big a deal is it- are you making it bigger then it should be to deflect or cover up the past?
You may be reacting because of either or both and are not even be aware.
When you have time reflect back..live and learn. That is what life is all about.