Why are people so wicked to one another ?

You have no idea what wicked is.

It's about power, diff-rent.
So much is.

There is a lot of wickedness in the world, Diff, no doubt about it. Most wickedness in my opinion is down to ignorance. One point about your original example though mate: If you find yourself in prison then all bets are off, being nice ain't gonna do you any favours in that situation.