How can an apostate be engaged in dialogue and brought back to Islam, especially when doubts have taken root in his heart regarding issues such as the capturing of women, fighting in Islam, and the 'awrah of a female slave? And how can it be proven to him that Islam is true, and should he be hated and treated with hostility if he is not convinced?

We have previously outlined the approaches to inviting atheists to Islam. You can refer to related fatwas and to the "Al-Kashif" website, which contains a complete file on misconceptions and their refutations, including those of atheists, secularists, and modernists.

Among the useful booklets are: "How to Invite Atheists to Allah Almighty in Light of the Qur’an and Sunnah" by Dr. Saeed Al-Qahtani, and "How to Invite an Atheist" by Midhat Hassan, both of which are available online.

As for the Muslim's stance on someone who leaves Islam, you can refer to previous fatwas on this matter.