I'm not bashing the fact that they don't have a book...I know all about the Yazidis situation. The fact that they are being persecuted confirms my statement. When you don't have a concrete, written set of rules, it's difficult to get other people to accept you.
I'm not saying you can't have religions without scripture, I'm simply saying that the vast majority of people need a physical, written dogma.
No offense intended.