What do the samurai mean when they say to be a good samurai you need to have black blood
It really is "For a Samurai to be brave, he must have a bit of Black blood." It is a ancient Japanese proverb, used in an assessment of the African presense in Japan.
You need to be born fighting you have to be very involved with it from the start.
The reference to black blood is could be compared to a sort of black heart. It has no racial or African meaning.
Black is Black (African) you really can't deny it.