I do believe that humans have intentionally attempted to reduce the risks of having sex. We have in particular invented several kinds of contraceptives, condoms, spermicides, and vaccination with the conscious, deliberate intent of making sex less dangerous.

I understood all of that, you were quite clear about this in your post. You think that the danger of sex is biological and that this has been vanquished by vaccines, condoms, etc. In reality, most of the power of sex to harm is social, emotional, and psychological. You are feigning expertise, without even considering the emotional, psychological, and social ramifications. It is pretty common to see this kind of shallow, hyper-atomistic (not considering ramifications upon society), reasoning on Less Wrong.

I do, sincerely and wholeheartedly believe that the vast majority of humans, regardless of age and gender, would lead better and more pleasureful lives if they had sex more often, with less guilt, with less fear.

There is substantial evidence that sexually promiscuous people (distinct from people who have frequent sex) are less happy. It is also a fact that married people have more sex (and more varied sex) than demographically comparable singles. Since married people are also significantly happier and report better health, it seems likely that it is not sex *itself that causes people to be happy, but rather that people who are in stable, happy relationships are also having more sex. Yet your post instead argues that people should just have more sex (including casual sex with strangers, multiple partners, etc.), ignoring the vital element of being in a stable, long-term relationship--in spite of the fact that promiscuity actually is associated with lower happiness. This is inexcusable. Do not give advice about topics when you have such a shallow understanding.