You get evil points by building a nuke, killing enemy soldiers a lot and kicking D-Dog among other possible actions that I've not yet discovered.
Once you enter demon mode the shrapnel will grow big and you will permanently be covered in blood, showers don't remove it.
you get evil points for killing with the knife , but I 'm not sure if that counts for weapons .
or build nuclear weapons later are also points .
But it is Kind of a temporary fix, because you can't finish the Story, this will just block everything that would Trigger it. If you want to finish the Story you will loose a Buddy forever and Play the game without it.