If you're a God of love, why send someone to Hell?

I think the difficulty of this question lies in our understanding of God. We are told that God is a God of love and this is true, but that is not all that God is. We must also realize that he is holy, righteous, and just. As much as God is love, he is also just as holy. As much as God is merciful, he is also just as righteous. As much as God is forgiving, he is also just as righteous.

What this means is that in knowing that God is holy, we should also ask why God should allow anyone in to Heaven who has sinned against him? If God is righteous, then how can we who are unrighteous expect to avoid Hell?

The truth is that since God is holy and just, those who disobey him must be punished. Otherwise, he would not be just. Suppose that someone broke into your house and stole your most valuable possessions. Thankfully, three days later this thief was caught and appeared before a judge. You wait anxiously for justice to finally be handed down when the unthinkable happens. The judge lets this criminal who ravaged through your house go without any penalty. The one who caused tremendous cost to you now go free. This all due to the judges decision. Now what would you think of this judge? Would you think he is just? Why not? Isn't he just being loving?

When we say that God is just, he cannot overlook the wrongdoing we have done in this world. If he did, he would no longer be just. But because of the grace, mercy and love of God, he sent his Son to be the one who paid the penalty for our sin. God cannot let sin go unpunished. Therefore, Jesus went to the cross for it as at the cross that justice and mercy meet. 

It is written in 2 Corinthians 5:21 that for our sake he [God] made him [Jesus] to be sin who knew no sin, so that in him we might become the righteousness of God. God has made the provision that was needed! Will you trust in what he has done? Will you believe in what Christ did on the cross? For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God (1 Corinthians 1:18)