Conversation so far:
What event did Phelps do to win his seventh gold medal?
100m butterfly
who did Michael Phelps beat in the 100m butterfly race at the Beijing Olympics?
Milorad Čavić
was there any other swimmers mentioned that Michael Phelps beat in the 100m butterfly race at the Beijing Olympics besides Milorad Cavic?
No
What other significant facts can you tell me about the 100m butterfly race at the Beijing Olympics that you found interesting besides who Phelps beat?
Čavić prompted the Serbian delegation to file a protest.

Question: Why did they file a protest?
Self-contained rewrite: Why did the Serbian delegation file a protest after the 100m butterfly race at the Beijing Olympics?