Somethime it has nothing to do with courage. It may have to do with "If you don't do something, you may feel ashame for the rest of your life."
"Fight you may lie, run you live, at least for a while."
http://www.youtube.com/watch?v=WLrrBs8JBQo
When a guy attacks a girl, your friend said, "You are a TCMA guy. Are you going to do something about it?" Either you will let your friend to laught at you on your face for the rest of your life, or you take action and have to deal with whatever may happen.