Jews - "the Torah specifies no minimum age for sex with a girl-child, and the Talmud's minimum age is three."?

May well be true. Haven't read the Torah. If it is true, why do so many people keep going on and on about Mohammed having 'taken' a 9 yr. old/12 year old wife (there are variations).? Christianity and Islam are both based on the 'Old Testament', yet many people use erroneous information about Muslims, which probably stem from the Old Testament as a weapon against Islam.