Never saw friendship as being a set of rules set in stone. Friendship comes and goes and can change so quickly. Why apply an absolute constant to what could be a quickly changing dynamic at any given time?
I remember a discussion like this held some time back. My answer is still the same. I view being a friend in the manner that I'd wish myself to be treated. If I'm doing something that's overly harmful to myself or others around me, I'd expect a friend to step in and knock some sense into me based on their discretion and judgement.
There are some things you overlook in friendships, because you can't change people no matter how hard you try on that particular subject. And for other things, you put your foot down.
It's important to be flexible, not rigid.