This is a very fair question!
My first point is that God doesn’t send anyone to hell; people send themselves there. God has revealed himself decisively in Jesus of Nazareth, via the biblical record, and in the physical world. Likewise God has installed a moral compass in all of us which bears witness to his existence. The Apostle Paul says that “They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them” (Romans 2:15). And since God’s power is so decisively demonstrated in the physical universe we are without excuse:
“For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse.” (Romans 1:20)
Ultimately we all know that God exists; some try to deny it while others look for God in the wrong places. In other words, people freely send themselves to hell for rejecting God’s gift of salvation through Jesus Christ.
My second point would be that for some people it would be the most loving thing for God to do. Why? Because many people who freely reject God don’t actually want to be with God. If they did not want God here on Earth then they certainly won’t want him for eternity in heaven. Would they be happy if God forced them into his presence? No, they wouldn’t & God would violate their freewill. In that way it would be God honouring their decision to reject him. Remember that hell is not a place where God tortures unbelievers; instead it is eternal separation from him.
A third point is that justice demands it. Would we consider it just of God to not punish those who have inflicted the most heinous of crimes on others in history? Hitler? Stalin? Rapists? Paedophiles? Terrorists? Should they just get off free? Surely not; if God just ignored the acts of such people (acts we all know ought to face punishment) would that be at all loving of him? No, it wouldn’t.
What we all need to take out of this is that Jesus Christ stands at the very center of history demonstrating God’s love for us. It was through Jesus that God “gave His only begotten Son, that whoever believes in Him should not perish, but have eternal life” (John 3:16). Through Jesus, God has made salvation possible for all those who will believe (John 14:6). Do not doubt. Believe (John 20:29).