Unfortunately, often people that argue against "God" and "hell" haven't read the Bible. "The existence of a plain where people are tortured forever for mistakes" shows that you haven't read the Bible either. The Bible states that "hell" is the eternal fire prepared for the devil and his angels. It was not prepared for man. The Bible states "The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance." 2 Peter 3:9. God wants ALL of us to have eternal life with Him.
Every single one of us has sinned and God provides a remedy for that sin and that is via a relationship - not religion - with Jesus. He would prefer we ask for forgiveness for the sins we have all committed and have a relationship with Him. This relationship provides a free gift of salvation - a gift we cannot earn by being "good" because none of us are. It is a gift free for the taking. However, we can choose to receive or deny this gift.
God respects and honours our choices - even though He wants us to have relationship with Him. Jesus said " Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me." John 14:6. A relationship with Jesus is the way to the Father - the way to heaven. If you reject that then you are choosing not to go to heaven.
Ray Comfort has an analogy that explains it well - If a man jumps out of a plane without a parachute, he will perish because he transgressed the law of gravity. Had he put on a parachute, he would have been saved. In one sense, he perished because he didn’t put on the parachute. But the primary reason he died was because he broke what has often been called “the law” of gravity.
If a sinner refuses to trust in Jesus Christ when he passes through the door of death, he will perish. This isn’t because he refused to trust the Savior, but because he transgressed the Law of God. Had he “put on the Lord Jesus Christ” (Romans 13:14), he would have been saved; but because he refused to repent, he will suffer the full consequences of his sin. Sin is not “failing to believe in Jesus.” Sin is “transgression of the Law” (1 John 3:4).
Sadly, people will be in hell, not because God puts them there, but because they reject the remedy. Heaven is not a place filled with "good" people, but forgiven people..