Huh. A headscratcher isn't it.
Here are my thoughts based on things I've picked up.
I kind of have this idea though, that if someone rejects god, they are rejecting themselves, as they are orientated toward God. their dignity; their goodness, they have rejected all of it. So theirs nothing there.
So they are unable to enter into loving communion with God and others. It has to go both ways for love to work, so it doesn't.
Another thing. Sadness can be descibed as an emotion that happens when we percieve injustice. So God would only be sad If hell wasn't just. and God promises perfect justice.