It certainly does sound racist.
From the Urban Dictionary:
2. Birfday: The ghetto version of “birthday”
Why you sleepin wif so many hoes on my birfday?
3. Birfday: An African American word for birthday.
Natasha gave birf to her 3rd child on her 17th birfday.
5. birfday: The way some uneducated black people pronouce the english word “birthday”.
yo its mah birfday dawg u kno wat im sayin
6. birfday: how a black person says ‘birthday’
“Yo man, it’s muh birfday taday.”
Since “Birfer” is most certainly a pejorative - “having a disparaging, derogatory, or belittling effect” - it’s interesting that the after-birthers (and particularly Fogblowers) would choose to use the pronunciation of the word most typically associated with belittling and disparaging the predominantly black, ghetto, dialect (Ebonics).
They are very comfortable in their racism.