Here's a question for you guys. Imagine you are in charge of creating a world with little people in it. They're just like you and me except that you have to look inside a microscope to see them. That's how small they are. So they can't see you, and you have complete control over their world. You are, in a sense, God.
You want them to be happy, to get along, be intelligent and productive. You want them to make children of course, so they can pass on their genes and the population will grow.
You set the laws and morality for this world. Now you're about to decide what these are going to be for sexual behavior, and how these little people view sex. Is it taboo? Is it completely open? You have no problems setting the rules for eating (people are free to watch anyone eat, people can eat in groups, talk about what they ate to anyone, express their food preferences, even buy food whenever they like, or purchase different toys that allow them to enjoy food even more, like special forks, beautiful porcelain plates, etc...). In fact, you allow for great food discussions -- detailed ones among people of all ages. You don't allow, however, stealing food from others because that makes it difficult for these people to get along. Now think about sexual intercourse. Like eating, it's a necessary biological function (in this case for the continuation of the species). Are the rules the same? Refrain from arguing from a religious perspective and concentrate on pure logic (understand that students on this board will be both religious and secular, but you must convince everyone). Just think of the logical moral standards and laws you might incorporate that you will feel comfortable with and will make this world work. Now compare these rules to the ones we live with in our society. Which of them are important and why?
No need for lengthy answers. A paragraph will suffice