1. The rational choice is to be a socio-path (by which I mean acquiring great skill at manipulating people through both logic and emotion).
2. After becoming a socio-path the rational choice is to use the new-found skills to manipulate key-players in the local environment to become rationalist so as to increase predictable courses of action. {EDITED} 3. Anyone holding political offices ought to renege on their right to privacy so as to make knowing their utility preferences easier.
3. Massive indoctrination at any kind of public education is highly desirable as long as this indoctrination is done thoughtfully and instilling the right drives and values for society optimization.
4. Women wanting insemination should only get seamen from men who've shown skill. Couples needing eggs; the same for the women donating.

About some of the other comments: Bestiality is legal in Denmark (hence I s'pose very far from being taboo). Prostitution is legal in Holland (and partially in Denmark) (also not taboo)

{ADDED} [I think all 5 of these qualify to being taboo in our current day and age and are silenced in our society for the very same reason; logical counter-arguments can, but are not, made]

I've retracted this comment due to me not actually thinking it will aid anyone in the long run; nor does it further the promotion of my own values and as Percent_Carbon points out it (and many like it) might end up harming LessWrong way before LessWrong achives a lot of the good I believe it capable of.