Okay, imagine you and your friends are playing a game of tag. In this game, nobody is allowed to touch the tree in the middle of the yard because it's like a safe zone. But one day, somebody decides to change the rules and says that they can tag you even if you're at the tree.
Now, you might think, "wait, that's not fair!" That's because it's not. But sometimes, people in charge make rules that aren't fair, and it can be really dangerous.
When people say "it can't happen here," they mean that bad things sometimes happen in other places, but they believe that the place they live in is too good or too safe for anything bad to happen.
But the truth is, bad things can happen anywhere if people don't work to make sure everyone is safe and treated fairly. It's important to always be aware of what's happening around us and to stand up for what's right, even if we think it can't happen here.