Why is everyone frightened of being "waited for by the young men"?

Everyone is frightened of the young men because they stand waiting for victims to rob and murder.

"The moment that the bus moved on he knew he was in danger, for by the lights of it he saw the figures of the young men waiting under the tree. That was the thing feared by all, to be waited for by young men. It was a thing he had talked about, now he was to se it for himself."

"His wages were in his purse; he could feel them weighing heavily against his thigh. That was what they wanted from him. Nothing counted against that. His wife could be made a widow, his children made fatherless, nothing counted against that. Mercy was the unknown word."

Freddy's father is the man who was attacked.... and the man who killed Freddy.