Honestly I think alot of people would just try to justify it. Someone yeu don't like? Well murder is now a permanent option! Sure yeu maybe wanted to hurt them before, but yeu would've gotten in trouble for it, despite that they probably deserved it. Now, without restrictions, there's no reason NOT to do so!
People tend to hate each other, often with little to no reason. They hate so strongly they're often willing to kill even when it IS illegal. Often, the fact that it's illegal is the only thing holding people back and making them grit their teeth, because they know they'd get in as much trouble for it; remove that and they lack that necessary hook to keep them from going too far.
Yeu want to see a good example of whot happens when the law disappears? Check out a major natural disaster. Looting, vandalism, murders, without a penalty, people tend to figure it doesn't matter.
They'll steal pens from work, because they justify it in their mind. And they will kill other people, because they justify it in their mind. The severity of the infraction honestly doesn't matter; the only difference is the severity of the punishment, which prevents some things more than others.
There's alot of people who WON'T do that as well, but there's far too many who can, and would, work themselves into some insane delusional self justified killing spree, simply because they think they're right and that the group they hate just has to die. Be it god's plan, racism, or whotever excuse they go for, they will do so.
It's best we don't remove the one thing that is stopping them from saying "God's will changed the law so that we could smite the sinners". We have enough nutjobs with enough munitions to level a small country as it is >.>