If you feel that sex is obscene, perhaps.

Edit: Otherwise I don't see what the goal does to make the butchery of your fellow man any more or less obscene than it inherently is.

I assumed he was gesturing at the creation/destruction discord inherent in sex/war with war being the referent for obscene. Of course, a full account of sex more than kisses and pleasantries, it also involves competition.

The (oftentimes sublimated) drive to procreate is one of the most powerful drivers of all human society and action. Perhaps even THE "primus motor" behind it all.

In Prometheus Rising RAW mentions that the reason monks take a vow of chastity is because it instantly frees them from one of the major hamster-wheels of the human condition.

Of course, I'm not planning to become a monk :) But food for thought...