Is the whole "Golden Ratio" thing a bit brutal, measuring whether someone is interesting by that metric? Well, yes - but life on Twitter is brutal :)
I think we all do it subconsciously anyway when we check out a person's account: do other people think you are worth following too? It's a good indicator.
Remember that newbies sometimes have a low ratio too, and people you are related to and can't unfollow, or people you work with who would get offended if you unfollowed them.
So just hide the newbies and the friends. Protect newbies because their ratio will grow. Maybe.