Greetings,
It's a serious question worth considering. There's no getting away from the fact that sexual ethics differ in different parts of the world, and according to different traditions.
Many people in the West do object to adultery and fornication, whether they are religious or not. However, it's also true that some people do act as if having limitless sex is perfectly OK.
Religious groups tend to frown on permissive sex, with varying levels of prohibition depending on the religion. At the same time, non-religious people can tend to view religious prohibitions as repressive or puritanical.
So we all have to find a way to accept each other's different views, because
1. These different views exist.
2. We humans exist.
3. We humans (I hope) would like to carry on existing, so let's not harm each other over it.