I'm a little surprised that the views are so strong concerning the sanctity of a church. A college professor friend of mine has spent a good portion of his career exploring eroticism (hetero- and homo-) in religious art (poetry, painting, sculpture). It's amazing how over-the-top dripping in gushing torrents of purple passion much of what is now looked at as classic religious art (and, presumably, sterile due to its religiosity) once was. There are even some saints whose religious revelations were likely more auto-erotic obsessions (based on things like Jesus' passion, bodily wounds, etc) than saint-like behavior.

That said, in college, one of my paramours and I had some multi-orgasmic frolics in what was once a congregational chapel that had long-since been de-sanctified and was used as a college meeting/performance space. Still had the taboo feeling (especially since we had to break in to access it).