Conversation so far:
What event did Phelps do to win Michael Phelps's seventh gold metal?
the men's 100-meter butterfly.
who did he beat in that race?
US born Serbian swimmer Milorad Cavic.
was there any other swimmers mentioned that he beat?
CANNOTANSWER.
What other interesting fact can you tell me about that race?
Phelps's seventh gold medal of the Games tied Mark Spitz's record for gold medals won in a single Olympic Games.
How did he feel about that?
"Dream as big as you can dream, and anything is possible ...
What other significant facts can you tell me about that race that you found interesting?
Phelps's 0.01-second finish ahead of Cavic 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 Phelp's 0.01-second finish ahead of Cavic?