Framing it as designed to ensure the dominance of one sex and one "race" is not doing the argument any favors. If that is what they set out to do, they did a poor job at it (even the Swiss and Kuwaitis suppressed their women "better") in addition, today, there exists slavery to this day in Chad and DRC, despite it being technically illegal. That argument is further eroded by claiming it's imperfect in enabling a promise. The constitution itself is what gave us the the necessary rights (including freedom of speech itself) to right previous wrongs.
Moreover, you can have a perfectly nice constitution guaranteeing all kinds of rights and freedoms like the USSR did (and I suspect the CCP does) and not enjoy the important aspects enshrined in such document)
But that's a misdirection in any case. It's utterly authoritarian to have a government decide what is truth and what isn't. That's one of the first things authoritarians go after. We should be very weary of anyone espousing the view government should have that right.