The Quran is a religious text and like many religious texts has bits of wisdom and insight.
I'm not gonna sugar coat anything and tell you there aren't parts of the Quran that aren't violent, but these aspects were meant for a different time, place, society and different circumstances.
For example tell your friend that in the Quran, Jesus is mentioned more than muhammad. We have a whole chapter or Surra called Surrat Maryam or the Chapter of the Virgin Mary. It is dedicated to Jesus's story. We have the stories of Adam and Eve of Noah and Moses and so on. The Quran should just be taken in context as a religious text, like the Torah and the Bible.
Unfortunately some extremist muslims try to draw upon violent meaning of the Quran and interpret them out of context to fit their agenda. Its just their way of politicizing religion to gain personal power and legitimacy a good example of this would be Anjem Choudary, someone who knows nothing about religion (He was a pot smoking, alcohol drinking typical college kid growing up) and is using it to legitimize his fanatical hate group.