The plea may be made that a loving Father would not see His children suffering the punishment of God by fire while He had the power to relieve them. But God would, for the good of His subjects and for their safety, punish the transgressor. God does not work on the plan of man. He can do infinite justice that man has no right to do before his fellow man. Noah would have displeased God to have drowned one of the scoffers and mockers that harassed him, but God drowned the vast world. Lot would have had no right to inflict punishment on his sons-in-law, but God would do it in strict justice. {LDE 241.2}

Numbers
35:15 These six cities shall be a refuge, [both] for the children of Israel, and for the stranger, and for the sojourner among them: that every one that killeth any person unawares may flee thither.
35:16 And if he smite him with an instrument of iron, so that he die, he [is] a murderer: the murderer shall surely be put to death.
35:17 And if he smite him with throwing a stone, wherewith he may die, and he die, he [is] a murderer: the murderer shall surely be put to death.
35:18 Or [if] he smite him with an hand weapon of wood, wherewith he may die, and he die, he [is] a murderer: the murderer shall surely be put to death.
35:19 The revenger of blood himself shall slay the murderer: when he meeteth him, he shall slay him.
35:20 But if he thrust him of hatred, or hurl at him by laying of wait, that he die;
35:21 Or in enmity smite him with his hand, that he die: he that smote [him] shall surely be put to death; [for] he [is] a murderer: the revenger of blood shall slay the murderer, when he meeteth him.
35:22 But if he thrust him suddenly without enmity, or have cast upon him any thing without laying of wait,
35:23 Or with any stone, wherewith a man may die, seeing [him] not, and cast [it] upon him, that he die, and [was] not his enemy, neither sought his harm:
35:24 Then the congregation shall judge between the slayer and the revenger of blood according to these judgments:
35:25 And the congregation shall deliver the slayer out of the hand of the revenger of blood, and the congregation shall restore him to the city of his refuge, whither he was fled: and he shall abide in it unto the death of the high priest, which was anointed with the holy oil.
35:26 But if the slayer shall at any time come without the border of the city of his refuge, whither he was fled;
35:27 And the revenger of blood find him without the borders of the city of his refuge, and the revenger of blood kill the slayer; he shall not be guilty of blood:
35:28 Because he should have remained in the city of his refuge until the death of the high priest: but after the death of the high priest the slayer shall return into the land of his possession.
35:29 So these [things] shall be for a statute of judgment unto you throughout your generations in all your dwellings.

No one is denying what the OT says. The mistake that is made is making it the gospel rule, God's ideal will, failing to see it is God meeting the people where they were. Jesus in the NT said that we are not to fight was not espousing a new rule, but a revelation of the truth as it was in the beginning. Why do want to stay in darkness? "Oh, that men might open their minds to know God as he is revealed in his Son!"

Christ as manifested to the patriarchs, as symbolized in the sacrificial service, as portrayed in the law, and as revealed by the prophets, is the riches of the Old Testament. Christ in His life, His death, and His resurrection, Christ as He is manifested by the Holy Spirit, is the treasure of the New Testament. Our Saviour, the outshining of the Father's glory, is both the Old and the New. . . . The Old Testament sheds light upon the New, and the New upon the Old. Each is a revelation of the glory of God in Christ. Both present truths that will continually reveal new depths of meaning to the earnest seeker. {FLB 12.5}