It is very common these days to think that God is such a nice guy He could never toss anyone into Hell. I had that idea once too. But this is just a gut reaction you get from people. If you actually think about Hell, hell, it's a good idea!
There are three ways to look at the need for hell. First of all, Christians (especially in the US) emphasize that this is a sin, that is a sin and the other thing is a sin and even one little sin is enough to get you into hell. Well, this is true, but this doesn't EXPLAIN hell. Atheists always object that a God who would torture you forever is just not a very nice guy and so either He doesn't exist OR if He does exist, they don't want anything to do with such a bad guy. Since even one tiny sin will get you into hell FOREVER, atheists say that just isn't fair. They'll say the punishment should fit the crime. Of course the answer here is that nobody does just one tiny little sin. Sinners have a selfish nature that produces sin after sin. You get to Hell for that overall selfish nature and not for just one tiny little sin. Christians don't always mention that.
The second way to look at hell is this. What do we here on Earth do with people who refuse to behave themselves? The worst ones, the thieves, the murderers, the rapists and so on all get locked up in prison where they can't do any damage to the majority of people who pretty much behave themselves. God simply takes this idea one level further. Everyone who has even the slightest inclination to be selfish, proud, arrogant, greedy and so on, would, if they arrived in Heaven, ruin the place for everyone else. The only way Heaven can be heavenly is if only perfect people get in. So that's what God does. He only lets perfect people get in. You might think that this excludes absolutely everyone but it doesn't. God will make you over into a perfect person if that's what you want. And the makeover is a free gift.
The third way to look at hell gives you the best understanding of what God is really up to. It starts out with God is a nice guy and He'll give you whatever you want. But the first question on the wish list is: "How do want to relate to everyone else?". There are only two choices. Choice number one is to put yourself first and do whatever YOU think is best for YOU. Everyone who is old enough will inevitably do this. God knows you will. He wants you to learn about selfishness. He wants you to see that a world full of selfish people is a mess. There is just no way to fix it. He wants you to notice how bad other people are. And, of course, He wants you to notice how bad YOU are. Atheists often complain about natural disasters like earthquakes, tsunamis, floods and terrible diseases. They figure He should not allow these disasters. But in these cases God is saying, "Oh, so you don't want me around? OK, fine, YOU take care of all these problems, they're your problems now". So overall, God wants you to see what a world without Him is like.
Choice number two is to humble yourself and listen to God and do what He wants you to do and then things will turn out well for you and for everyone else. God does, after all, have plans that are good for you and everyone else. He really just wants to make everyone happy!
But what happens if you make choice number one where you just decide to have things your own way? You are, in effect, saying "God, I don't need you so just leave me alone and let me run my own life". Well, He will leave you alone. Atheists always complain that if there is a God He ought to show himself. But if you don't want anything to do with Him, just why should He show Himself to YOU? Shouldn't He just let you go on thinking that He isn't there? This is, after all, exactly what you want!
But now, if you never, ever, ever, want anything to do with God, what should He do with you? Well, it's easy. He won't give you a nice big house on a nice little planet. He won't give you a job, a car, a vacation or anything at all! Why should He? Your highest priority is that you don't want to have anything to do with Him! Then what if He went against your wishes and tried to give you and everyone else who doesn't want anything to do with Him nice things anyway? It would be just like Earth only worse. Everyone would be hating and fighting each other and all the nice things would just end up getting destroyed.
Then there is the idea that Hell is burning with fire and brimstone. Now I have no idea if the following idea is true, I have never found this anywhere in the Bible so this is just a guess. Here on Earth we have people who "get all steamed up", get "hot under the collar", are "hotheads", are "burning with anger" and are "burning with hate". So I strongly suspect that the fires in Hell are caused by the people who are there. They're burning with hate for their fate, burning with hate for God and burning with hate for their neighbor. They're creating the flames themselves.
So even with a burning hot Hell that lasts forever, God is still a nice guy. He's giving everyone EXACTLY what they want. Either a world with Him or a world without Him. If giving everyone EXACTLY what they want isn't fair I want to hear about it!