Matthew 23:33 What is the "Condemnation of Hell" that Jesus was Warning the Pharisees about?

Around AD30, several days before His crucifixion, Jesus warned the Pharisees about the impending destruction of the temple in Jerusalem in Israel.

Among other things, Jesus said, "Serpents, brood of vipers! How can you escape the condemnation of hell?" He continued to tell them, "Assuredly, I say to you, all these things will come upon this generation." (Matthew 23:33-36)

What was Jesus referring to when He warned the Pharisees about the "condemnation of hell"? I think it is important for us to understand Jesus' words in the proper context because mainstream or evangelical christianity has been using the term 'hell' loosely to refer to a physical place in the afterlife, reserved for unbelievers and sinners, to be burnt and tortured for eternity. This misunderstanding only serves to misrepresent God, painting Him as a petty and tyrannical judge who is far worse than an errant parent on earth.

The Greek word for "hell" in the above passage is "gehenna", which refers to the "garbage dump in Jerusalem that burns for a period of time". It is an allusion to the destruction of the temple in Jerusalem that would take place in AD70. My understanding is that Jesus had warned the Pharisees about the condemnation of gehenna in the last days. (Matthew 23:33)

While the law ended at the cross, the Pharisees didn't believe that, and had a 40-year grace period to repent (change their mind and believe the good news of grace). The old covenant officially ended in AD70, with the destruction of the temple, and there would be no more sacrificial system. 

The Pharisees probably experienced condemnation in their minds or in their conscience, thinking that it was the end of the world for them, and mistakenly thought God was punishing them. I think that was the gehenna Jesus was warning them about. The judgment was in their mind, but God wasn't the one judging them - their own conscience judged them. (Matt 12:36) They experienced the second death by coming to the end of themselves. Without the physical temple, there were no more opportunities for them (if any survived the seige) to depend on sacrifices or rituals to make themselves righteous. That's my understanding for now.

How do we know the old covenant had passed away?

We read in Hebrews 8:13 "In that He says, 'A new covenant', He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away." The author was telling the Hebrews that the old covenant was ready to vanish away. The book of Hebrews was said to be written around AD63-64. It would only be a few more years before the old covenant age would finally end in AD70, ushering the new covenant age, in which we all are living today.

It was a revelation to me when I realised that Jesus' reference to gehenna was addressed to the unbelieving Pharisees, which they would experience in their conscience when they mistakenly thought that there was no more opportunity to get close to God or to be right with God, when the temple crumbled before their eyes. It must have been a huge shock and disappointment for them - they would certainly have felt lost and completely alienated from God because they and their previous generations had been so dependent on their religious performance and rituals and the animal sacrificial system in the temple for the past hundreds of years in order to be righteous or to connect with God (or so they thought). Hence, Jesus had been telling them to repent (change their mind and believe the good news that the kingdom of God was already within them, not outside of them), in order to escape the condemnation of gehenna (in their conscience).

(This post is based on a discussion thread about preterism in Facebook.)