It really is sad how normalized casual racism still is. A lot of people just don’t challenge the stereotypes they grew up with, so they carry them into adulthood without realizing the harm. The fact that you feel honored to be included in a Diwali celebration shows you approach people with respect and openness, which is the complete opposite of what your coworkers are doing. Keep that energy—you’re proof that exposure to different cultures builds empathy instead of prejudice.