Because i feel with how society today is that they just don't wanna talk about it. Or it gets too religious. But it was afterall a big political unity before reformation and age of enlightenment came forth. So one can sorta use that to learn from those mistakes, that still exists in other parts...
If you read "Book 56 Jihad" and "Book 64 Military" in Sahih al-bukhari there is plenty of stuff that justifies terrorism and glorfies martyrdom.
And hostile views against unbelievers you can find in the quran. Surah 9 is btw taken in context, it was revealed in 630 AD in our calendar. Just...