If you only want to believe in some aspects of the True Living God, but reject other parts of Him, by rejecting the other parts, you’re committing the sin of idolatry by creating a god in your mind that suits your personal tastes; putting yourself in the judgment seat instead of the Lord Jesus Christ.

The Bible says there is one God in three persons, the Father, the Son, and the Holy Spirit. (Heb 1:8, Act 5:3-4, etc) Often, I see people, condemning or scoffing at the God of the Old Testament.

Howbeit in vain do they worship me, teaching for doctrines the commandments of men.
-Mark 7:7

I will say this very clearly at the start: The God of the Old Testament books and the Jesus Christ of the New Testament Gospel are one and the same, and to reject one is to reject the other in turn.

God is righteous. (Ezr 9:15)
God is holy. (Isa 6:3)
God is forgiving. (Mat 6:14)
God is jealous. (Exd 20:5)
God has loved mankind. (Tts 3:4)
God hates sin and the wicked. (Pro 6:16-19)
And more specifically to this topic: God is just. (Deu 32:4)

In the Bible, when God gives people a long time to repent of their evil and wicked ways, mankind complains about it. When God immediately punishes people for their evil and wicked ways, mankind complains about it. It doesn’t matter what God chooses to do, mankind will mope and whine about it.

We need to understand that when God chooses to punish a wicked people, it is justified in every case. For example, God commanded the nation of Israel to exterminate the Amalekites, down to the last man, woman, child, and beast. (1Sam 15:2-3) When scoffers of the Bible mention this commandment of God, they claim how horrible it is that God would allow this, however, when put into the context of the history laid out in Scripture, the Amalekites were a wicked people that plagued God’s chosen people for hundreds of years with war and disease! They were also warned to repent and turn from their wicked ways, or face God’s judgment. I’m glad I’m not God because I don’t think I could be that longsuffering. The Lord allowed an evil people to last MANY generations because:

The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance.
-2 Peter 3:9

Even when we look at the book of Jonah, God was set to destroy 120,000 wicked people in Nineveh, but he sent Jonah to preach and warn the people of God’s judgment. The city, along with their king, took Jonah’s warning seriously, and immediately, the entire city fasted and prayed to God for forgiveness and repented of their sin. God showed Nineveh mercy. Nineveh’s people were terribly wicked, and Jonah knew this, so when God showed them mercy:

But it displeased Jonah exceedingly, and he was angry.
-Jonah 4:1

Mankind whines and complains when God shows mercy to sinners, yet, when the Lord decides their time is up and punishes sinners, mankind whines and complains about that too. It seems mankind just wants to whine and complain.

The fact that a man would scoff at God for a decision to wipe out a wicked people shows how completely selfish and ignorant we have become. When a man stands up and says that a decision of God was wrong, he claims that he himself is more righteous than the All-Powerful Living God! That’s incredibly arrogant! People are trying to judge God, when God is the only reason we have justice and morality to begin with. God is good and the standard for goodness, and we can’t use the standard for goodness to say the standard for goodness is not good. That’s nonsense. We need to humble our hearts before All-Mighty God, repent of our sins, and give thanks for the long-suffering He has endured with us and our stupidity.

God is both just and merciful.

If you want to believe in a god that is forgiving, but not judging, then you believe in a false god. If you want to believe in a god that is loving, but will not punish sinners, then you believe in a false god. (And because God and Christ are One, you believe in a false christ!) We have to accept ALL of God, or in reality, we accept NONE of Him. People are always deciding to take what parts of the Bible they are willing to accept, throw out the rest of God, and break the 2nd commandment, making themselves idolaters.

Did God allow forty-two children to be killed for mocking His prophet? Yes. Why? I don’t know, and won’t claim to know. Perhaps the Lord knew that wicked generations would arise from these children, causing more suffering and death in later generations, so He decided to stop it before it started. Perhaps they made habit of mocking God and His prophets to tempt His anger. We don’t know why God chose to allow this. We only know the children were doing a wicked deed, and they were punished for it.

With that in mind, we know there is an age of accountability spoken of in Scripture, where little children, who have not reached an age of knowledge of good and evil, are not sent to hell upon death. The 2 bears killed 42 “little children,” and thus, it is likely that these children didn’t understand what they were really saying and who they were saying it to, but they were trained by their society to do and say such things against the prophets of the Lord, so if the children went to heaven when they died, who was God really punishing? I suspect that God was really punishing the parents for teaching and allowing the mocking of the Lord.

When God chooses to punish sin, we don’t have a right to question it. Again, God is the standard for right and wrong. To question God’s authority over morality would be to claim oneself as a moral authority, which ends in logical fallacy no matter what arguments are made.