Sin is not something inherited, one man is not accountable for another man's sin, the soul that sinneth it shall die meaning wach man is accountable for his own sins....."Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression..." Rom 5:14. If death is a result of all inheriting or being held accountable for Adam's sin then all die as a result of that one, same exact sin, yet Paul makes a distinction in showing people died as a result of sinning a sin not after the similitutde of Adam's sin, they died as a result of their own sinning.
You cite Rom 5:12 that ends by NOT say 'because all inherited Adam's sin', but instead ends by saying "because all sinned" which shows personal culpability in people choosing to sin different and various sin from Adam's sin. In the first 3 chapters of Romans Paul goes to great length to prove all, Jew and Gentile have sinned. In Rom 3 Paul cites many verse from the OT that proves the Jews were sinners as much as the Gentiles. Yet no where in these chapters does Paul even remotely elude to the idea that all, Jew and Gentile, were innately born sinners. Instead Paul proves they are sinners by citing transgressions Jews and Gentiles have committed for sin is transgression of the law (1 Jn 3:4) and not just an idea or substance that is passed between people.
Adam nor Eve were created sinners but created with a free will and told and knew what God's law was to not eat of a certain tree. They chose to sin by eating of that tree and then by committing that transgression they became sinners. Likewise we today follow in the steps of Adam and Eve in that we are not created/born sinners but have a free will and have been given God's word (Bible) and can learn and know God's law but then choose to sin against that law and then we become sinners. Since sinning is a willful choice, (not necessary due to how one is innately born), then God can rightly, justly condemn the choices man makes for himself.
