@Boqor
You're an intelligent man. Use that brain of yours. Is there no way to punish a criminal except by fire? When was the last time you saw a rapist being burned at the stake? What does auto da fe have to do with criminal justice?
I will give you some arguments from the Quran, Sunnah, and Islamic scholarship that support the sheikh.
Bear this in mind though: The Quran makes it clear that some verses are metaphorical. It says for instance "hold on to the rope of Allah". There is no rope to grab on to. That's a metaphor. It says the unbelievers are "deaf, dumb, and blind". They're not literally deaf and blind. That's a metaphor. It says that "Allah is closer to you than a jugular vein". If you take that literally it means that Allah is inside your body. He isn't. The Quran is filled with metaphors and allegories. I could go on and on. Even the most basic and central elements of theology are draped in metaphor. For instance Allah is called a "He". In everyday language, the male pronoun "he" refers to a man with a penis, but Allah is not a man, and he does not have a penis. It's a metaphor. It's just how Arabs speak.
Firstly, the Quran says that Christians, Jews, and Sabeans will go to Paradise.
Secondly, the prophet said a prostitute who fed a cat went to Paradise even though she was spreading fitna and fasaad across the earth.
Thirdly, another hadith says a man who killed 99 people went to Jannah after repenting of his ways. Most non-Muslims don't even kill a single person, but you believe the Most Merciful and Compassionate is gonna torture them forever?
Fourthly, a hadith says that Allah's mercy always triumphs over his anger.
Fifthly, every sura of the Quran except suratul Tawbah begins with "Allah is the most merciful and the most compassionate". There's a reason for that. Mercy is the most central element of Allah's character and the one most emphatically stressed again and again. Not his wrath, but his mercy.
Sixthly, it is unjust to punish somebody eternally for sins that were not eternal. Infinite punishment for a finite number of sins cannot be defended morally. Proportionality is a key requirement of justice. A just magistrate would not send a shoplifter to thirty years imprisonment for stealing a candybar. That would be disproportionate and excessive, so why would Allah do something which even human beings can see is wrong.
All of these arguments, when taken together as a whole, bear out the scholars who argue that hell is not a literal place, but a state of mind.
There are verses in the Quran that show hell is metaphorical. Give me a while to dig them out.