People with those kind of arguments always get from response that if you were not trying to keep in touch with this friend personally then it was not truly a friend. Facebook friends does not equal real life friend.
Sometimes it's not about closeness. It's about people's expectations about how to communicate. My cousin was in no place to do anything but post to Facebook and then collapse. My sister helped him, but didn't think to tell me because you know Facebook. I live 4 hours away so I wouldn't have learned by osmosis.
I have several stories of learning about deaths in the family way after the fact because my family is chronically on Facebook and I'm not. They all live in my hometown and it just doesn't occur to them to actually communicate with members like me who don't live there.
This is basically why I haven't deleted my Facebook even if I don't often log in.