Casual and even seasoned readers of the Gospels are impressed by Jesus' message of love, forgiveness, mercy, and care for each other. So, when they stumble on passages like the one from today (Lk. 14.25-33) they sit or stand stunned for a moment asking themselves, "Wait, did I read that right???"
It does seem contradictory, begging the question that if the Gospels were so heavily edited for content how did THAT sneak in? How could the one preaching love for neighbour, forgiveness, care for the poor, then tell us if we don't hate our parents, siblings, spouses, even our very lives, we then cannot be His disciples?
Apparently the Early Church had a tradition, a midrash if you will, to explain this. St. Augustine, St. Basil the Great, St. Gregory of Nyssa, St. Symeon the New Theologian, Tertullian, Origen (among others) all weigh in on the matter and they have these to offer:
OF COURSE we should not HATE our families, but we need to be absolutely CERTAIN that the relationship does not get in the way of our relationship with God (um, idolatry folks...)
These relationships are TEMPORAL only, the only relationships surviving the Resurrection being the brotherhood/sisterhood of believers (which family members can of course share).
As disciples of Jesus Christ our first duty is to leave everything behind to follow Him: relationships, possessions, honour, position, you name it.
Some of this may seem counter to our popular theology, but the point is that the eternal relationship that matters, that will last past our deaths and manifest again on our resurrection is the relationship with Almighty God. We are called first and foremost to discipleship and to the work of the Kingdom of God, and blessed are those whose relations are on board with the same program. That hearkens back to another saying of Jesus:
"“Who is my mother, and who are my brothers?” And pointing to his disciples, he said, “Here are my mother and my brothers! For whoever does the will of my Father in heaven is my brother and sister and mother.”' (Mt. 12.48b-50)
Discipleship calls for a single-mindedness, a willingness to let go of anything that gets in the way, that prevents love for neighbour, mercy to the needy, hope for the hopeless. That is the highest calling, and happy are those whose nearest relations share in that calling.