Orthopraxy III - Remembering What Amalek Did

This is the third post in the series exploring whether halacha (and specifically halacha which is relevant today) requires belief or just action. That is, can someone who does not believe in God or who does not believe in the historicity of the Torah still keep all of halacha, and thus be Orthoprax? Or does part of the prax involve dox? Are there mitzvot which can only be when one believes?
(part 1, part 2 of the series)

The next commandment I want to consider it the positive Biblical commandment to remember what Amalek did. There is a pasuk in parshat Zachor, at the end of parshat Ki Teitzei, and the Rambam considers this a commandment. To cite him, in his hakdama to mitzvot aseh, he writes:

קפט לזכור מה שעשה עמלק תמיד, שנאמר "זכור, את אשר עשה לך עמלק" (דברים כה,יז).ר

And in sefer shoftim, hilchot melachim, perek 5, he writes:

ה וכן מצות עשה לאבד זרע עמלק, שנאמר "תמחה את זכר עמלק" (דברים כה,יט); ומצות עשה לזכור תמיד מעשיו הרעים ואריבתו, כדי לעורר איבתו--שנאמר "זכור, את אשר עשה לך עמלק" (דברים כה,יז). מפי השמועה למדו, "זכור" בפה; "לא, תשכח" (דברים כה,יט) בלב, שאסור לשכוח איבתו ושנאתו.

Thus we see that it is a mitzvah to always remember Amalek's evil deeds.

This implies that one believes that the evil deeds mentioned in Torah indeed happened. This typically entails belief in Torah. One who believes it to be a myth cannot remember what they did. He can remember that there is a myth that they did X.

Furthermore, the Rambam continues with something mippi haShemu'a - (perhaps Torah sheBaal Peh, or as halacha leMoshe miSinai backed up by asmachta from the pasuk) - "Zachor" is to mention it in one's mouth. "Lo Tishkach" - "do not forget" is in one's heart, for it is required to maintain a specific emotional state regarding Amalek.

This is based on Megillah 18a, embedded in a discussion about whether one fulfills reading the megillah by merely thinking about it, and they want to show that actually reading it is required. To that end, they discuss Zachor and what it means in terms of Amalek.
[דתניא] (דברים כה) זכור יכול בלב כשהוא אומר לא תשכח הרי שכחת הלב אמור הא מה אני מקיים זכור בפה...

Thus, clearly, we have a halacha that involves internal thought processes and beliefs. Thus, halacha does sometimes mandate certain emotions or beliefs - things internal to one's heart/mind.

Can someone who does not believe Amalek did anything - because the Torah is a fictional account - can he really have these emotions? Can he be said to be actually remembering anything?