I can understand the idea of what you are saying, although I have a slightly different view. I do not think that sex and nudity rely on marriage to be 'pure' or 'clean'. For starters, these words are subject to interpretation, their meaning is not specific. But how I see the quality of a thing or an act is based in the consciousness or mentality of those involved.
So for instance, if two people are in a long term relationship with every intention of being together, respecting and loving one another for their lives, then this is beautiful whether they are married or not. Marriage is a legal binding only, or the meaning of marriage is dependent on the culture of where it occurs.
Then you can have a married couple who hate each other, are abusive, lack respect and love for one another and then the relationship is not beautiful, it is not 'pure'.
If somebody is taking advantage of another person for sex, it is not beautiful. But if a person is having sex with great love and care for the other person, then it is wonderful no matter if a ceremony has occurred or legal papers have been signed.
And I could not think of someone as 'dirty' for simply not being virgin. Life is not so black and white. Everything is dependent on context; time, place, and circumstance.