Is it wrong to look at nude preteen girls?

It depends on your outlook. In today's society it is considered immoral to be sexually attracted to a teenage girl. However, if you look back at the majority of human history, as well as simple anatomical facts, you would see that females are most fertile before they reach the age of 20. Tens of thousands of years of genetic evolution has wired our brains to be attracted to youth, in the interest of the longevity of our species.

Secondly, the human lifespan has more than doubled in the past 300 years. Before modern medicine, human life expectancy was somewhere around the age of 35. This means that in order to raise your child into adult-hood, most people were having children around the age of 15.

When compared to the entire span of human existence, the whole concept of "being sexually attracted to youth is evil" is extremely recent.

Personally I find nothing wrong with finding teenage girls attractive, our brains are imprinted to do so.

That being said, it is not longer necessary to engage in sexual activities with young girls due to our increased life expectancy, and modern society has expanded our innocent years, making sexual experiences potentially traumatizing for young girls, whereas before we would prepare women for the beginning of their menstrual cycle, which once started, means they're ready to have babies.

Thoughts and looking are one thing, acting on them to the detriment of a young girl's well-being is entirely another.

On a side note, I find it incredibly ridiculous that 15 year olds are being put on sexual offenders lists for having a picture that their 15 year old boyfriend/girlfriend texted to them.