why do people get so angry?

About a month and a half ago me and one of my bestfriends Terrance got in a pretty huge arguement. It all started at like 11:30 on a friday night. First we started talking about our purpose in life and I told him I feel called to Missionary work and he was like no you don't know what God wants bla bla bla he doesn't just speak it into your ear! and I was like no but I gave him a verse that says if you need wisdom ask your generous God and he will give it to you, he will not rebuke you for asking. and he flipped out! The point of me telling him that was that if he was unsure about his calling in life to ask God to reveal it to him. But instead he flips out and starts yelling at me about how I don't know anything about the bible and I shouldn't be quoting stuff I don't know anything about and how it has a deeper meaning than that. So we ended up getting in a heated discussion and I said how God is unchanging Malachi 3:6 and then he said that God didn't write the bible but I told him he annoited people to write about him and he said how do you know and I explained that Exodus 17:14 says how God commanded Moses to write and it was just rediculous.. we argued until 4:30 in the morning and the next day he says to me, "I knew you were right, I just didn't want to be wrong because I felt you were belittling my knowledge of the bible" I was so shocked! I couldn't believe all that time went by for no reason just because he felt like I had offended him when in reality I was trying to encourage him!