Hyde inside everyone of us?

I just watched an interesting document about aggression and violence. I don't take myself for a violent person at all. I get dizzy when I see blood or broken limbs, nor could I ever punch someone on purpose. Not really hard anyway. I don't particularly enjoy violent games, movies or sports either.

But so thought the man in that document. However, when he was put through a couple of tests he found out that violence is actually a part of him too. He got really paranoid due to lack of sleep and admitted having felt a little pleasure when managed to hit a man with whom he was fighting.
He also spoke with a few specialists who told for example that our control over aggression can easily crack. For example in a serious car accident the area of our brain which controls our feelings and impulses can be damaged and change our personality. I think it's really scary that we are that fragile. That the part of me that I think is permanent, my personality, the real me, can transform into something unrecognisable. Makes me think about Dr. Jekyll and Mr. Hyde.
What if there really is a brutal beast hiding inside everyone of us?

The most shocking thing of all was a psychological test, in which the subjects thought they were participating in a memory test. With every test subject there were two actors, one playing another subject and the other playing a professor. All the test subjects had a role of a teacher and they were supposed to read word pairs on a list while the actor playing another subject played a student (getting complicated??). "The student" was to memorize the words "the teacher" was reading aloud. Now, every time "the student" made an error "the teacher" was told to give them an electric shock as a punishment. Each shock was five volts bigger than the former. The biggest possible shock was the lethal 450 volts and the main goal this test was to find out how many would actually kill  another human being in the name of science.
If the test subject playing a teacher hesitated or wanted to quit the professor told them to continue because it was important.
What's really frightening is that 9 over 12 subjects kept going giving the electric shocks till the end as they were told to.

I find the result rather horrific but it does explain something about Nazi-German and that kind of stuff. Violence is really a part of humans whether we acknowledged it or not. And anyone could do the most terrible things under pressure.
I just keep hoping I'd have the guts to say no.