@Chaylev Halyah: Did I say that Christianity is shituf? Did I say that they use Shem Shamayim?
No, I didn’t. I just quoted the Rema in Shulchan Aruch. There are others who disagree. See the explanation of Rav Ovadia Yosef who explains those who disagree with the Rema. Does your Rov rule like Rav Ovadia? OK. Does he rule like Rema? OK.
Again, don’t mix your own ignorance into the discussion. This is not a shouting match between missionaries and yeshiva bochurim in the street outside yeshiva on Thursday night. We are discussing the various halachic opinions on the matter.
No matter what, it is obvious that the evangelicals are wrong in their beliefs and especially wrong for trying to get Jews to follow their beliefs. At the same time, it is very good that they are strongly involved in the Sheva Mitzvos and making the world a better place according to the morals and values given by Hashem in His Torah. Even regarding the first of the Sheva Mitzvos, there are opinions that it is not so bad for them.
When Moshiach comes, they will be the most ready (from the goyim) to accept him and realize that they were fooled by their forefathers about many religious ideas. (רמב”ם הלכות מלכים פי”א ה”‘ד)