Racism is the belief in the superiority of one race over another. It may also include prejudice, discrimination, or antagonism directed against someone because they are of a different race or ethnicity, or the belief that members of different races or ethnicities should be treated differently. Modern variants are often based in social perceptions of biological differences between peoples.
as salam alaikum
in the mentioned case, it is imperative to do "Amr bil-Ma'ruf wa Nahy 'anil-Munkar" to denounce their attitude and try to rectify their behaviour. However one needs to find the most appropriate way to do it without worsening the situation.
With prayers for your success.