Why did this put me off so badly?

see my friend lets call her miranda* we came m8s again after soo long see about an hour ago we was talking on messanger and i talked to her on how fb is evil and how my reasons for it brings sadness she agreed in some ways she said it creates fights on there with people she even said she likes arguing with people cuz she likes taking her feelings out on people she hates i even said i hate arguing its not cool to fight and you see ages ago we had a fight on her mates profile so i said to her so thats why we argued on ya mates profile last time because you wanted to take your anger out on me? and she said well to be honest if im in a very bad mood i will take my feelings out on someone i hate i said okay then ( <<< i said that to hide my pain ) then she went silent why did that make my heart sank like now why i do feel upset n hurt because of what she said im being serious by the way it hurt me so bad why did this put me off so badly like my heart is in my mouth :'( :( i almost cried i now feel like i cant talk to her anymore i hate the sort of people who like arguing it sad isnt it lol sooo just tell me why has this put me off so badly? and dont answer if youve got nothing nice to say!