Is a son considered sinful for hating his father who wronged him and seized his money, despite the son's attempts to treat him kindly and not disassociate from him?

What the father did regarding the car was an injustice to the son. It is incumbent upon the son who took possession of the car without a legitimate right to return it to his brother, its rightful owner, because it is akin to usurped property that must be returned to its owner. Hating the father due to his disobedience is permissible and entails no sin. It is worth noting that hating a disobedient father does not contradict showing him filial piety and kindness, as Allah Almighty says: "But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them, but accompany them in [this] world with appropriate kindness."