To regard the body as impure—or anything as impure—is a limited and dualistic perspective. Purity and impurity may appear as definite separate states, yet we can quite easily understand—with a little investigation—that purity or impurity are only relative definitions based in a particular view.
From the perspective of Vajrayana there is no pure or impure – everything is available for transformation. Tantra begins with the experience of emptiness – the pregnant space from which form arises. Form is simply that which arises – and does not need to be viewed in terms of pure or impure. Human bodies are as they are and are available for appreciation.
Samsara is not a separate existence to nirvana. They are the same experience – it is view that changes.