No, it is not ethical at all. Humiliating someone based on any physical characteristic is a form of body - shaming. Everyone should be respected regardless of their body type, and spreading such stories can cause great harm to a person's self - esteem and mental health.
If you come across such stories, don't share them and encourage others not to as well. Also, promote positive body image campaigns to counter such negative ideas.
In my opinion, it depends on how it is presented. If it is done in a way that objectifies or degrades people in a way that could potentially harm real - life individuals or relationships, then it is not ethical. But if it is used as a means to explore themes like jealousy, power dynamics, and the complexity of sexual relationships in a fictional and thought - provoking context, it might be more acceptable, but still controversial.
Rather than exploring humiliation stories which are not positive, we could look at stories of healthy communication and mutual respect in relationships. For example, there are many tales of couples who overcame difficulties through open and honest dialogue.