That same passage also says to call no man teacher, but then what are we to call those who teach us? If we are to call no man father, then what are we to call the men that raise us? No matter what word you use, they’ll all have roots with those two words. Whether you use the term doctor, professor, they mean teacher. Daddy, papa, again mean father. It isn’t meant to be taken so strictly. All it means is that you only have one Heavenly Father, God, and only one Heavenly Teacher, Christ.