R' Chaim Brisker held that according to the Rambam a denial of the ikkarim due to misunderstanding is still considered apikorsus -- it is not the crime of denial which defines one as a heretic (in which case the context and cause of the crime would be relevant considerations), but rather it is the affirmative belief in the ikkarim which defines one as a member of the Jewish people. Excuses cannot subsitute for the affirmation of belief.
My son is learning Perek Cheilek and I noticed an interesting chiddush in the Birchas Avraham (Sanhedrim 91) based on this approach. Since the ikkarim must be affirmatively believed, he writes that there is an obligation of chinuch to teach children before bar mitzvah the meaning of the ikkarim so they understand and accept these beliefs. Unfortunately, most schools do not have a curriculum designed to accomplish this goal (yes, parents can do it, but parents can also teach kids gemara, halacha, and Tanach and schools go over that). It would be a nice idea for someone to pull together a program aimed at elementary school age children to accomplish this goal.