Hadith on someone biting their father's genitals

Can someone shed some light on this hadith: > Ubayy b. Ka‘b told that he heard God’s messenger say, “If anyone > proudly asserts his descent in the manner of the pre-Islamic people, > tell him to bite his father’s penis, and do not use a euphemism.” > > Mishkat al-Masabih Vol 2, 1021