Burden of Proof

[Surtr]

I don't believe that just being an athiest on earth would preclude someone from heaven

You don't agree with your own bible.

Mark 16:16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned.

Matthew 10:33 But whosoever shall deny me before men, him will I also deny before my Father which is in heaven.
Matthew 10:34 Think not that I am come to send peace on earth: I came not to send peace, but a sword.

If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, which is as thine own soul, entice thee secretly, saying, Let us go and serve other gods, which thou hast not known, thou, nor thy fathers; Namely, of the gods of the people which are round about you ... Thou shalt not consent unto him, nor hearken unto him; neither shall thine eye pity him, neither shalt thou spare, neither shalt thou conceal him: But thou shalt surely kill him; thine hand shall be first upon him to put him to death, and afterwards the hand of all the people. And thou shalt stone him with stones, that he die. -- Deuteronomy 13:6-10

For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. -- 2 John 7

Although as Catholics we have a concept of Purgatory which softens that a little but doesn't fully deal with it.

"Soften" it all you want, you can't justify infinite punishment for finite human sin.