Is the category of Apikores- a heretic only limited to Jews or even non Jews?
The Sdei Chemed quotes many opinions that forbid quoting from heretics
Thus, is it permitted to quote a heretical gentile that preaches that Judaism is false? Or that there is no world to come. May I quote a wise saying from Muhammad that has nothing to do with theology per se', for since Muhammad denied the truth of the the Torah and its accuracy if he were a Jew he would be classified as an apikores.
(I know that the source for the word apikorus is really the name of a greek philosopher Epicurus)
a) one who says Torah, even one verse or one word, is not from God. If he says: "Moses made these statements independently," he is denying the Torah.
b) one who denies the Torah's interpretation, the oral law, or disputes [the authority of] its spokesmen as did Tzadok and Beitus.
c) one who says that though the Torah came from God, the Creator has replaced one mitzvah with another one and nullified the original Torah, like the Arabs [and the Christians].
– user6591 Jun 16 '15 at 13:27