Ki Teizei: Could Bilaam's curse or blessing harm or help?

Summary: According to Ibn Caspi, no. This was catering to the superstitions of the hamon am.

Post: In the middle of Ki Teitzei, we read:

4. An Ammonite or Moabite shall not enter the assembly of the Lord; even the tenth generation shall never enter the assembly of the Lord.		ד. לֹא יָבֹא עַמּוֹנִי וּמוֹאָבִי בִּקְהַל יְ־הֹוָ־ה גַּם דּוֹר עֲשִׂירִי לֹא יָבֹא לָהֶם בִּקְהַל יְ־הֹוָ־ה עַד עוֹלָם:
5. Because they did not greet you with bread and water on the way, when you left Egypt, and because he [the people of Moab] hired Balaam the son of Beor from Pethor in Aram Naharaim against you, to curse you.		ה. עַל דְּבַר אֲשֶׁר לֹא קִדְּמוּ אֶתְכֶם בַּלֶּחֶם וּבַמַּיִם בַּדֶּרֶךְ בְּצֵאתְכֶם מִמִּצְרָיִם וַאֲשֶׁר שָׂכַר עָלֶיךָ אֶת בִּלְעָם בֶּן בְּעוֹר מִפְּתוֹר אֲרַם נַהֲרַיִם לְקַלְלֶךָּ:
6. But the Lord, your God, did not want to listen to Balaam. So the Lord, your God, transformed the curse into a blessing for you, because the Lord, your God, loves you.		ו. וְלֹא אָבָה יְ־הֹוָ־ה אֱלֹהֶיךָ לִשְׁמֹעַ אֶל בִּלְעָם וַיַּהֲפֹךְ יְ־הֹוָ־ה אֱלֹהֶיךָ לְּךָ אֶת הַקְּלָלָה לִבְרָכָה כִּי אֲהֵבְךָ ה אֱלֹהֶיךָ:
7. You shall not ever seek out their welfare or their good, all your days.		ז. לֹא תִדְרֹשׁ שְׁלֹמָם וְטֹבָתָם כָּל יָמֶיךָ לְעוֹלָם:

This seems to ascribe some sort of reality, and efficacy, to Bilaam's potential curse, and to his actual blessing. But if Hashem is in control of the fate of the Jewish people, why should any curse have impact? For example, Hashem would decide whether they won any given battle. Why hold this grudge against Moav for attempting some superstitious thing which would not work, and why did Hashem transform the curse into blessing because of His love for us?

Ibn Caspi explains that Hashem was catering to the ignorance and superstition of the masses:

כִּי אֲהֵבְךָ ה אֱלֹהֶיךָ  -- אין בקללת בלעם ולא בברכתו ממש
על דרך האמת, אמנם המון ישראל אז לסכלותם היו נמשכים כי יש
ממש גדול בדבריו אם לרעה אה לטובה, לכן שמרם השם מהזק על
ידו, אף היטיב להם כי ברכם:


"There was not  in Bilaam's curse nor his blessing any substance, by way of truth. However, the {uneducated} masses of Israel at that time, in their foolishness, were drawn into believing that there was great substance to his words, either to bad or good. Therefore, Hashem protected them from 'damage' via his actions, and even made it better for them, for he {=Bilaam} blessed them."

Ibn Caspi does not use the term of dibra Torah kilshon benei adam here, but it is a similar idea. Not just in narrative but in direct address, they are spoken to as if things which are not true are indeed true. For previous instances of this approach, see Ibn Caspi and the Magic Trumpets and Hashem testing you with false signs.