If the Spirit of the Lord abides in a man he will leave Islam faster than you can say: "come out from among them"
And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people. Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you, And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty. (2Co 6:15-18 KJV)
God works in different degrees among people, even Christians. I know of many Christians who appear much more holy than I am, even some Protestants. God gives us a number of gifts, one of which is faith. Normally, God does not, though, infuse the knowledge of revelation to a man - He leaves that to His Church to proclaim the Word. (Romans 10) Thus, a Muslim could do loving things because of the Spirit, but not be aware of Who is leading Him, nor be aware of the Truths of Christianity (since the Spirit is not often discerned from where He came - like the wind). Since SOME Muslims DO convert, one must presume that God is working among them when a Christian evangelizes or speads the Gospel. Normally, that is how people become Christians, when they hear the Word proclaimed.
Naturally, converting from Islam is not so cut and dried like it is here - often times, converts family's outcast them and often try to kill them. It takes a strong faith from God to overcome this "obstacles" to the Faith, wouldn't you agree?
Regards