How is Mecca forbidden to Jews and Christians, where is religious tolerance in that, how do we respond to those who say this, and how can some of the "People of the Book" be Muslim and yet forbidden from entering Mecca?

Allah has forbidden Mecca to every disbeliever. There is no correlation between a disbelieving woman having a Muslim son and her entry into Mecca. A Muslim man marrying a woman of the People of the Book is one matter, and a disbeliever entering Mecca is another. Jews and Christians are not followers of Moses and Jesus (peace be upon them) due to their distortion of their religions. The phrase "religious tolerance" is intended to negate the principle of al-wala' wal-bara' (loyalty and disavowal).