Whether a person should have known better or not doesn't change the fact that these bad people shouldn't be doing these bad things. I don't know why or how it

Whether a person should have known better or not doesn't change the fact that these bad people shouldn't be doing these bad things. I don't know why or how it got fashionable to dismiss someone having something terrible done to them by saying "they should have known better" but every single time it's bullshit. I have a feeling it's a thought terminating cliche to help out of the state where you know something terrible happened to this person, and there is nothing you can do about it.