As I've previously said, you have a point - interpretation is important.
What you seem to be ignoring is content. It's a simple fact that in the Quran (and Hadiths) there is plenty of violence, cruelty, bloodshed and killings - either on the battlefield or as capital punishment.
Here's a thought, what if literacy improved in the Muslim World, ordinary people read the Quran for themselves and decided on a literal, violent interpretation. There's no Muslim equivalent of the pope to correct them.