Marrying a young girl (litterally: becoming master of the girl) is not
illegal in the Old Testament, Islam, Vedic tradition, nor is it illegal in
other eastern belief systems.
It is illegal in the global religion that the United States and Britian has
foisted upon the world and maintains through mandatory schooling, bombing,
and economic sanctions.
You believers in that religion do not allow any other religions or law
systems to exist in the world. You use your power to create hegemony and are
in a constant battle against other religions/law-systems which have little
hope of holding their own against yours.
You have the bomb. You have the military. You have everything. And you're on
crusade.