It is forbidden to stare at a pretty woman, even single, or a married woman even if she's ugly (Avoda Zara 20a, on the bottom). The Yeatzar Hora (Satan) will try to mess you up with a married woman even if she's ugly. So obviously it's OK to stare at an ugly single girl since she won't turn you on. The Talmud is talking about all these things that would turn you on, like "it's forbidden to stare at animals having sex."
So if you can't look at an 8 year old girl then she's obviously turning you on. We can now look forward to a whole new generation of Chasidim who will look at child porn the second they get their hands on the Internet, and you can expect child rape to go up. where are you Nachum Rosenberg?
A girl came on a crowded bus in Jerusalem together with her boyfriend and there was no place to sit. What did she do? She stood (With her boyfriend) in front of a Haraidi guy (So he should get up from his seat and run away) but the guy didn't move. So she says "I thought you're not allowed to look at girls?" So he says "Zeh rock leyofim". "That's only for the pretty one's". (I heard this story from a friend of mine years ago)