Is the son's saying to his parents, "I wish you were not my parents in the Hereafter," considered an offense to them, despite their repeated mistreatment and distance from religion, and despite his patience and good treatment of them being for the sake of Allah and in hope of a better reward in the Hereafter?

The statement "I hope they are not my family" is offensive, especially towards parents. Allah commands good speech with people, encourages kind words, and emphasizes that speech should be gentle with parents. This statement is meaningless because Paradise removes resentments, and we should consider ourselves deficient in obeying Allah. We should not despair of our families, for perhaps Allah will guide them through us.