Balanced arguments are more persuasive

According to this summary of a meta-analysis, arguments are more persuasive when both sides are presented, even when preaching to the choir. This research explains why abstinence-only sex education --- which is still funded at $50 million per year and requires that only disadvantages of birth control and condoms be presented, not advantages --- does not encourage abstinence as well as comprehensive sex education does, even among those inclined to believe it, and why the only abstinence-only program found effective (the Jemmotts' program) was not one-sided enough to be funded under federal abstinence-only funds.