I don't believe that's the biggest problem. The main problem is what the Quran says and that people take it literally, as intended
You mean like this .........?
2:216 "Fighting is prescribed for you".
2:244 "And fight in the cause of Allah".
8:39 "Fight them until there is no fitnah and the religion, all of it, is for Allah".
8:65 "O Prophet! Exhort the believers to fight".
3:142 "Do you think that you will enter Paradise while Allah has not yet made evident those of you who fight in His cause".
3:169 "Never think of those who have been killed in the cause of Allah as dead".
4:74 "Let those fight in the way of Allah, who sell this world's life for the hereafter; and whoever fights in the way of Allah, then be he slain or be he victorious, We shall grant him a mighty reward".
4:76 "Those who believe fight in the cause of Allah, and those who reject Faith Fight in the cause of Evil: So fight ye against the friends of Satan".
4:84 "Fight then in Allah's way".
61:4 "Allah loves those who fight in His way in ranks as if they were a firm and compact wall".
61:11 "Have faith in God and His Messenger and strive hard for His cause with your wealth and your persons".
9:29 "Fight those who believe not in Allah".
There are more, but they can all be summed up by verse 9:111 - "Allah has purchased of the believers their lives and their properties; for the price that theirs shall be the Paradise. They fight in Allah's Cause, so they kill and are killed".
These verse, and others like them, are the reason Islamic jihad (we call it terrorism) exists.