"They went home and raped/beat their slaves, killed Native Americans for their land, and prohibited women from voting. Needs a bit of work in these modern times."
Unless there are provisions in the Constitution that explicitly call for these things, they cannot be cited in any argument either for or against the Constitution. A prima face case of apples and oranges.
What this is is a typical liberal ploy - the ad hominem. Since they can't discredit the Constitution based on what's written in it, they attack it by attacking the character traits and practices of the men who wrote it. Liberals always show that they can't win arguments based on the merit of their positions, because they have none - all they can do are throw cheap shots and make fun of people.
There is nothing in the Constitution that states that White men must own slaves, that White men must beat or rape their slaves, that Amerindians (or whatever you want to call them), and that women must not be allowed to vote. Those issues are ancillary to the Constitution and what's actually written in it.
Furthermore, we legitimately conquered the Americas from the Amerindians. The right of conquest gives us the right to inhabit this land. No one cared when Amerindian Tribe A conquered and dispossessed Native American Tribe B, so no one should care when Whites come in and do it to all of them all at once. Boo hoo.
Women didn't vote and didn't care to. They certainly didn't feel oppressed and certainly were not treated so.
As for slaves, they had it better on White farms than back in Africa, or even now, living in fear of their lives from their own.
Leave it to a liberal to miss the boat. Again.