And the same sorts of phenomena exist in Christianity. People abandon the faith all the time, in droves (honestly, the secular world has the most successful "da`wa," and while far more Christians have been swept away, Muslims in the west are starting to witness the pull of the secular world a bit too). Some Christians (not a majority, but nonetheless a bunch) who leave the faith wind up returning. Christians who belittled them or spoke negatively about them (in some of the same ways as described above) contributed zero to their return. On the other hand, Christians who continued to respect them, maintain friendships with them, and slowly have long on and off conversations with them (which could span months or even years) were significant factors in winning them back."
Come Back To Allah (Hamza Yusuf video)
Learn about Islam: