Slenderman just doesn't make sense. Why wouldn't he want for many people to see him? It just doesn't add up. If he does feed of our belief and fear, why wouldn't he just reveal himself in public so more people would fear him? And if he doesn't (Which I'm pretty sure he doesn't), why would he keep hidden? And why would he kill people that know about him?
...What if he's scared?
Maybe he knows that if he lets us live long enough, we'll spread the word. People will know about him and they'll want to kill him. Maybe he knows that if enough people attack him at the same time, he won't be able to defend himself. Doesn't that make sense? He might be stronger than us as individuals, but if we all come together we are bound to overcome him!
Now, I'm not saying that we should just gather up 50 Runners and charge at him, but if we attack with one organized, well thought and strong blow, we might stand a chance in combat. Hit him when he's the weakest (Maybe the next solstice? That'll give enough some time) with as much manpower as we can get.
There is a lot of planning to do... But I think we might actually have a shot with this plan.
Tell me what you think, and if you have any suggestions or information, I would rather appreciate it.