That's because you haven't had a Muslim try to convert you from Christianity to Islam, Use the Bible and the scriptures as your defense and that will be the 1st thing they use as an argument.... Ask any Muslim about the Bible and they'll tell you.
That's also because he doesn't understand Muslim history.
The Koran clearly has a simple three step plan to convert to Islam:
2. Pay a ransom.
Qur'an (9:29) - "Fight those who believe not in Allah nor the Last Day, nor hold that forbidden which hath been forbidden by Allah and His Messenger, nor acknowledge the religion of Truth, (even if they are) of the People of the Book, until they pay the Jizya(ransom) with willing submission, and feel themselves subdued."
Qur'an (9:5) "But when the forbidden months are past, then fight and slay the Pagans wherever ye find them, and seize them, beleaguer them, and lie in wait for them in every stratagem (of war); but if they repent, and establish regular prayers and practice regular charity, then open the way for them..." Prayer and charity are among the Five Pillars of Islam, as salat and zakat. See below.
Qur'an (9:11) - (Continued from above) "But if they repent and establish worship and pay the poor-due, then are they your brethren in religion" This confirms that Muhammad is speaking of conversion to Islam.
Qur'an (2:193) - "And fight them until persecution is no more, and religion be only for Allah. But if they desist, then let there be no hostility except against wrong-doers." The key phrase is to fight until "religion be only for Allah."