It's Briedis' life, he can do whatever he wants. He isn't hurting anyone. Singing a rap song, it will be a nice memory in his life. When he is an old man, he will look back and say: I did this in my youth days to fight a guy named Jack Paul. You live only once.
It s like when you see your fwvorite pornstar of gesteryear has become a homeless drug addict level of sadness.