1. The depth of love means that when the unforgettable love is lost or hurt, people often can't stand the blow, and complaints, sadness, regret, grievances and so on come out together. If there is no place to vent, it will naturally turn into bitter hatred.
2. Source. From Wuthering Heights, the extended meaning of "love and hate are cut off, and the scissors are still chaotic. Who can tell?"