The “not crying on Sundays” embodies the hopeful spirit that goes along with the song. Homosexuality will hopefully lose the negative stigma, and will not be seen as a sin by more religious individuals on Sundays (Christianity’s day of worship).
It’s singling out Christianity as the biggest voice in this battle. Many groups are intolerant, but in this issue, in this country, the Christian right is the main culprit (and then the oppressive rap culture referenced before).