This is my interpretation of the basic principles of Buddhism only. I'm no scholar on Buddhism or an expert on the writings of Siddharta Gautama.

The fundamental idea of Buddhism is that nothing on this Earth is permanent and that attachment to impermanent things leads to suffering. It is well-known that intimate relationships are often fraught with powerful emotions. Passionate erotic love is precisely the sort of thing apt to lead one astray from the Golden Path towards enlightenment, which is understanding the foolishishness of attachment toward such impermanent and transient things as erotic passion.