Converts and Christianity
The Torah gives very clear instructions as to how we are to treat the convert. It is speaking of the stranger who accepts upon himself to observe the 613 Mitzvot of the Torah.
We are not allowed to mistreat him in any way. We must be careful with our words not to insult him in any way. We are to remember that we were strangers in a strange land, when we lived in Egypt.
There is a story in Masechet Yevamot that speaks of a heretic who challenged Rabban Gamliel. He brought a source from the prophets that seemed to indicate that Hashem abandoned the Jewish people.
According to Rav Shteinzoltz, he was trying to justify Christianity, as being the new legitimate religion. Rabban Gamliel called him a fool and showed him that he misinterpreted that particular verse.
I have been working with converts the past thirty years, and the most prevalent reason for their deciding to convert, is based on this same contention of the heretic, but in the reverse.
They are troubled by the rebirth of the Jewish nation and the State of Israel. They ask their professors about this abandonment question. The Jewish people are not looking very abandoned these days. A Jewish population in Israel of nearly eight million, and an army that is looked at as a superpower, are just two of the reasons that disprove this theory.
And because their professors do not have a good explanation for the State of Israel, they decide to become part of the Jewish people. We are to love and embrace the convert, for choosing the more difficult path of truth, rather than live a life filled with contradictions.