There are many documented and studied cases where orders to carry out massacres which were disobeyed carried no harm to the German who refused.

Mostly demotion or transfer to a different area, but no execution or jail time. Sometimes not even that.

I'm talking about not taking part in massacres (e.g. shooting unarmed women and children, locking people in a barn and setting it on fire, etc), not about refusing to fight, cowardice, aiding the enemy or actual treason.