Shouting Boss???

My present boss is very nice to everyone. But in my previous company I had these frustrated woman I used to report to who would shout at everyone for no apparent reason.People would just maintain their own dignity and keep quite instead of going down to her standards of screaming at the top of the voice for silliest of reason. I think people who feel insecure do things like this. They feel that if they behave nicely to others, no one will give them respect. So they feel the need to scream at their subordinates to show their power