Jonny,
I find it hugely bizarre that you didn’t see the answer to your question in the passage. I’ve already dealt with this before so, I’m not going to keep going over it and over it, but here it is:
You seem to think that God is obligated to show grace to rebel sinners who don’t want to have anything to do with Him. This is bizarre. You know nothing about grace. Grace is unmerited favor and never owed to sinners. Hell is simply the just punishment of those who have been separated from God’s grace for eternity. Because they are separated from God’s grace (common and saving) they remain evil while in hell. Indeed, the longer one remains in hell the more hardened their heart becomes and thus, the more just God’s punishment of them is. Part of the justice of hell is God keeping evil’s harm and influence out of the new creation as God protects His children (the bride of Christ) from its destruction. The glory of God’s justice shines forever as He shows His tender love to His children. Moreover, this glory has been there since the beginning. God experiences all past, present, and future events as being “present” in His timeless eternal now. It’s this glory that God rejoices in. The glory of His beautiful mercy and justice. It’s not that He’s sadistic. For it’s not the suffering of those in hell in and of itself that God is glorified in. Rather, it’s His justice. God is eternal and therefore His justice must likewise be eternal. As the above passage states, all parts of His glory must shine forth so that His children may have a proper knowledge of Him. Thus, making their joy complete.