A friend of mine told me we don't have the obligation to apologize to a gentiles. Is this true?
הֱוֵי מִתַּלְמִידָיו שֶׁל אַהֲרֹן, אוֹהֵב שָׁלוֹם וְרוֹדֵף שָׁלוֹם, אוֹהֵב אֶת הַבְּרִיּוֹת וּמְקָרְבָן לַתּוֹרָה
Be of the students of Aaron: Loving peace and pursuing peace, loving all people and bringing them close to the Torah.
(Tractate Avot 1:12)
In fact, in addition to the basic human decency requirements, there are the additional issues of besmirching the people and G-d you represent by association (chilul hashem) as well as the problems associated with inciting antisemitism.