One of the most important concepts in Christianity is original sin or the belief that all mankind has inherited a sinful nature brought about by the acts of Adam and Eve.
Rom. 5:12 "Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:"
Rom. 5:19 "For as by one man's disobedience many were made sinners,..."
1Cor. 15:22 "For as in Adam all die, ..."
No amount of reasoning can make an inherently unjust idea seem right. Punishing billions of people for the acts of one is not only inherently unfair and
unwarranted but also in opposition to other Biblical verses such as:
Deut. 24:16 "The fathers shall not be put to death for the children, neither shall the children be put to death for the fathers (2Chron.25:54) :every man shall be put to death for his own sin." (2 Kings 14:6)
Ezek. 18:20 "The soul that sinneth, it shall die. The son shall not bearthe iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him."
Ezek.33:20 "O ye house of Israel,I will judge you every one after his ways."
Jer. 31:29-30 "In those days they shall say no more, The fathers have eaten a sour grape, and the children's teeth are set on edge. But every one shall die for his own iniquity: every man that eateth the sour grape, his teeth shall be set on edge."
Rom. 2:6 "Who will render to every man according to his deeds."
Ezek. 18:4 "... the soul that sinneth, it shall die."
Each of these verses shows that every person should only be punished for those sins which he commits, not those of others.
If you are to point out that 'every one sins', that would just point out that God, in His 'perfection' created us flawed and is punishing us for His mistake.