I actually have nothing against abstinence. I think it’s perfectly fine to teach children that abstinence is the most effective way to avoid STDs and unwanted babies.
The problem is, humans come in all shapes, sizes and…. life history strategies. Per Wikipedia, “A life history strategy is the ‘age- and stage-specific patterns’ and timing of events that make up an organism’s life, such as birth, weaning, maturation, death, etc”
Generally, people whose life history strategies are more future focused, such as those who place a heavy emphasis on savings and education, also tend to delay sex until later in life and have lower numbers of sexual partners. Meanwhile, people whose life history strategies are more short term oriented, with a heavy emphasis on immediate rewards, tend to have more frequent sexual encounters with a greater number of partners starting from an earlier age.
While certain life history characteristics tend to correlate together, there are also folks who display a mix of the above traits. For example, someone might place a heavy emphasis on the future but a low emphasis on commitment, so they have more sexual encounters.
Furthermore, it is theorized these traits also have a genetic and environmental component, which means that individuals don’t really get to choose their life history strategy. Like so many things, first nature has a go at us, then nurture has a go at us, and the final product is who we are whether we like it or not.
As a result, abstinence only policies that fail to teach other forms of birth control are guilty of not taking into account the great diversity of human life strategies. By not doing so, such policies in effect discriminate against some people whose life strategies (which they do not really get to choose) may make it more difficult for them to conform.
Maybe someday such advocates for abstinence only policies will wake up to the fact that people differ from one another, and that having only one kind of sex ed fails to take into account the great diversity in human sexual strategies. When that time comes, we can all develop more rational approaches to preventing unwanted pregnancy and STDs that celebrate, rather than reject, the diversity that exists among humans across ALL traits, including sexual strategies.