I still don't see the point.
If someone is bothering you, or you dislike a person - ignore
Also, just because someone is not on a "friend list" doesn't mean anything - it is just a list of people you want to know who is online when you are which makes it easier to talk to those people. I talk to WAY more people on a regular basis then who is on my list. By the way, my list is around 200 people the last time I checked & I talk to them ALL on a regular basis.
Now, unless you can come up with a better reason, I say this is a waste of time.