Retrospring isn't the best platform for me to give you context on how the concept itself of "demure" is a tool of white supremacy (thus antiblack) in our current (western) society, so I'll politely suggest you learn about the links between femininity itself and white supremacy and the way that black (femme) bodies are perceived under white supremacy. You can look up the treatment of Saarji Baartman her whole life (and even postmortem) and Caster Semenya as well and how black femmes specifically are violently excluded from the [gentle, meek & mild] perception of women/womanhood.

I hope that'll give you an idea on why [demure] is antiblack at its core (emphasis on at its core !!)