I agree, this topic is hard. I unfortunately opened up this can of worms with a disney movie, believe it or not. We watched the movie 'The Rescuers' and in it are 2 little mice who save a little girl named Penny from a character called Medusa and Medusa's mean partner. Medusa kidnapped Penny from an orphanage and made Penny look for a lost diamond. The plot made my daughter very curious and she talked about Medusa alot. I started having to elaborate on the movie and how mean Medusa is, and how kids that are kidnapped are not happy and are mistreated. It turned out to be kind of a good teaching tool and Penny is a little girl that young kids can relate to. Now, we will bring up Medusa when we feel like she's being unsafe in a public setting, or even at home. We will tell her that's why she can't be outside by herself, etc.
I hope this helps. We started watching the movie when my daughter was 3 and 3 months. You can only buy it so you might want to preview it from a friend if you know someone with it before you buy it.