I'm not surprised you've got a complex about hell. Probably so does all of Islam and Christianity.
"They also say that they are waiting for the day to see my skin and bones melt in hell while they are there laughing at me!"
- would that be good behaviour? No. Would that be mean and hateful? Yes.
I think there are maybe three or four reasons for it:
1) in-group / out-group bias. We all love and support the people in our group and really tend not to like the people in other groups. I think Islam is the most "them and us" out of all the religions.
Jean Decety writes in "Friends or Foes: is empathy necessary for moral behavior?":
It is well established that the mere assignment of individuals to arbitrary groups elicits evaluative preferences for in-group relative to out-group members, and this impacts empathy.
So we are actually less physically sensitive to the pain of out-group members, have less empathy for them, and therefore, following the Golden Rule, are less willing to help them.
2) Belief in God = belief in morality. Non-belief in God = "I am a baby-eating satan worshipper". But I think wanting to see your son melt in hell and laughing while it happens, falls into the latter category.
3) tradition and cultural practices have value in making society function cooperatively, and if you don't follow them, people feel like they can't trust you because you're not "playing the game" and acting like a functioning member of society.
4) suddenly you're free of the bullshit that they're forced to live under, and they're jealous.
Yeah, one of the hardest things is to deal with rituals people you love and want to stay close to value. When my family said grace, I'd hold hands and bow my head but not say "Amen," for example. Hope that helps.
When my father died several years ago, there was a Christian memorial service in. I did attend out of respect but begged out of any of the participatory ceremonies. Now, my family is pretty liberal and understanding, but not all are that way.