Before there was modern day government many countries used religion as the back bone for their laws. Much like the various races, nations, and political parties people by and far tend to have a "my team is better than your team" mentality.
If you don't believe what I believe than you are wrong or going to hell. Sometimes groups feel threatened and they attack each other. If everyone truly believed "Thy shall not kill" there would be no such thing as war, murder, abortion, suicide, or the death penalty. If we really bought into "Love thy neigbor as thyself" there would be no such thing as racism.
Deep down on some level everyone of us is a hypocrite. We tell kids they shouldn't lie and then we turn around and call in sick to skip work. We say it's wrong to steal and then turn around to claim tax deductions we aren't entitled to. We say follow the speed limit but if it's 55MPH we go 60-70MPH. We exchange wedding vows promising to be faithful and then we cheat.
Ecclesiastes 7:20 "For there is not a just man upon earth, that doeth good, and sinneth not." (There is a big difference between knowing what to do and doing it)