Cheez. Think about this.
We see The Silence every day, but we don't remember it. They are locked into the collective subconscious of the entire human race.
They don't wear our suits. We made our suits look like what they wear.
They don't look like generic aliens. The imaginations of the people who made up the generic aliens were just channeling the subconscious.
They don't look like Slenderman. Whoever made Slenderman up made him to look like them, subconsciously.
Think about that. And ask yourself: How many Silents have you killed today?