Seems to me I recall thousands and thousands of ethnic Chinese that were mass murdered in Indonesia not all that long ago historically, and it wasn't because of religion. It was because they were Chinese, period.

Ignorant and violent people can always find a handy excuse to kill their neighbours...regardless of what their religion is...as long as their neighbours are seen to be different in any way. The Chinese were hated for 2 very simple reasons:

1. They were generally good at running businesses and making money.

2. They were "different".

The reason those girls were killed was most likely because their killers saw them as "different". That's what is behind most such violence.