Category 4 and 5...
Not safe.
It's one thing to have sexual attractions. It's quite another to have a proven history of believing you're entitled to sexual gratification relating to those attractions, to the point of abusing and raping others or facilitating abuse and rape. And that is what having a conviction of possession of category 4 and 5 photographs of children being abused means.
He wasn't convicted for having nasty thoughts he couldn't help. He was convicted for his actions. Category 4 and 5 images don't download themselves into your computer.