I don't think anyone is going to think you are an awful person for looking for pictures of children. I can think of lots of perfectly innocent reasons why someone would need one (mostly having to do with art or advertising).

Conversely, I get a perverse pleasure out of searching for horrible things while on my University's internet. I figure if I ever have to justify it, I just say it's for work. It always is, anyway.

Last time it occurred to me, I was looking for images of bondage in advertising. Some pretty awful things came up!