In brief, the question about marriage to a minor is evidence of a selective of knowledge of the Talmud, and a total lack of knowledge of Talmudic logic and methodology as well as ancient cultural norms.
Talmud: The Talmud makes it clear (Kiddushin 41a): Rabbi Yehudah said in the name of Rav and some say it was Rabbi Elazar: “It is forbidden for a man to give his daughter in betrothal while she is a minor, until she matures and says, ‘I desire so and so’”
There is absolutely no other authority in all of Jewish history who disagreed with this opinion.
The reason the Talmud discusses the marriages etc. of minors is because in those days it was common for society to engage in childhood marriages. It was a combination of shorter life span and earlier maturity. Even in the nineteenth century is was common for families to marry of their sons and daughters around the age of puberty.
The Talmud deals with both the moral aspect of people’s behaviors and the legal aspect. This means very simply: If a man would betroth a 3 year old girl, while that would be immoral and against Jewish law, it was a legally binding union and they would require a divorce to sever that marriage. At no time did the rabbis sanction this type of arrangement despite the fact that it was widespread in ancient societies and was not viewed as a form of sexual deviancy.
Another example of the above is the discussion of polygamy. Although Jewish law did not prohibit it until about 1,000 years ago, it was almost non-existent among the Talmudic rabbis. What is legal does not necessarily mean that it is moral. And what is moral is not necessarily the ideal practice. Most of the Sages went beyond the norm of what was legal and beyond the minimum standards of morality.
As for their “obsession” with sexuality, the Talmud is Divided into 60 volumes. Each one discusses a different area of Jewish law. Jewish law governs every phase of life and seeks to address the legal and moral issues in those areas and to provide guidance in every aspect of a person’s life. This indeed is what Judaism is all about; not to escape the world and live like a monk but to engage it and elevate it by making every part of life holy by connecting it to a G-dly commandments. Of these 60 volumes there are 5 that deal with all aspects of marriage and divorce. That is about 8%. Of these 5 volumes one can find perhaps 10% that deal with sexual matters in a purely legal context. That means that far less than one percent of the Talmud deals with these issues and not in sensual and lascivious fashion. It is no different from a physician who discusses a woman’s anatomy ad sexual issues from a medical point of view.
A final point: The way the rabbis treated their wives and women in general is legendary and way ahead of their times. In fact, much more respectful than the norm today. Why don’t the critics of the Talmud cite Bava Metzia 59a, for example, where the highest standards of respect for treating a wife are discussed?