Juuzou was suspected to hurt pets because he is different to other child. In fact, it is a violent adult who tortured animals to calm his mood swings. Really, Juuzou is the character of Tokyo Ghoul who suffered the most. But without ever complaining.
Scars are the mark of strong person, they represent the endurance and strength you needed in order to withstand the physical or emotional abuse. That thing or person which tried to kill or weaken you, contrarily only made you stronger.