At the risk of starting another flame, I disagree that marrying a Christian or a Jewish woman is allowed in Islam. What the Quran has clearly allowed is marriage to chaste women (Al-Muhsanaat) of the People of the Book. Alas, chastity is very rare in today's world.
God has very specifically forbidden marriage to fornicating women,
"And the fornicating woman - none may marry her but a fornicating man or a polytheist, and that is forbidden to the believers." (24:3)
God has declared Chapter 24 mandated and its verses "manifestly clear", in its opening verse. This Chapter must therefore be taken very seriously just as God made it so serious.