Another moral could be related to the cycle of nature. The rooster is a part of nature and its interaction with the girl can symbolize how humans are also part of nature's web. We should respect all living beings and their natural behaviors. If the girl was initially scared but then learned to co - exist with the rooster's sometimes - erratic behavior, it shows that we can adapt and find harmony with nature.
I'm not aware of any specific "huge cock in tiny mouth stories" in mainstream literature. Most literature focuses on more positive, moral, and diverse themes.
You might discover a new style. For example, if your friend has a different fashion sense than you, the dress she puts you in could be something you would never have chosen for yourself, but end up loving.
Educate oneself about appropriate communication. Learn about the values of respect and decency. Also, if you encounter someone bringing up such inappropriate topics, firmly but politely let them know that it is not acceptable behavior.