Professor didn't want to change exam date (valid reason)

Hey, so I got my interview to get US citizenship and I talked to my professor showing him proof of everything. His answer was "I'm sorry, I have 200+ students and it would be difficult to accommodate you", I asked if I can take the exam on office hours where he said "No, but I can provide a letter for immigration if you want to reschedule your interview. Sorry I know this administration is difficult". I was shocked, and I didn't want to do. I contacted the dean's office, but this was very close to the appointment. As a result, I had to withdraw the class because this teacher just allowed one exam drop and I didn't want to risk it (had the oath ceremony after the interview, thought that it's always 1+ month and I could possibly miss the last exam). How can I proceed in those terms? I would like to warn other students and also take action against him (if possible). I sincerely believe that this is a racist act.

TLDR: I got a citizenship interview the same day as my college exam, and professor didn't want to reschedule it.