how might the course of American history have changed if the bill of rights had forbidden discrimination of all kinds and had protected the rights of minorities?

This is what we refer to as a counterfactual question in History. No one source is society can contribute to the alleviation of social ills. The Constitution did not recognize African Americans as citizens. Thus, as enslaved people they would not be guaranteed protections under the law. Native Americans and Hispanic Americans were also marginalized. Women, too, were marginalized. These protections would need additional legislation as well as a seachange in attitudes.