Inevitably, when this topic of discussion comes up, I almost always see a response of this type, calling into question the entire foundation of the USA on the basis of the founding brothers being white slave owners, and it really bugs me, but I'm having a hard time trying to articulate it well...
I think it mostly centers around a very superficial understanding of the evolution of the enlightenment and the renaissance into the culmination of those that was the US. I would probably respond better if, when these arguments get thrown about, I heard discussion of the philosophical underpinnings the founders, in particular Madison, based their proposals on. Discussion or reference to individual liberty, natural law and natural rights, and such, as learned from study of Socrates, Plato, Aristotle, Thomas Aquinas, Locke, Hobbes and Spinoza, Montesquieu, etc.
I almost never see these referenced in this responses though, and to me it seems very dangerously close to "throwing the baby out with the bathwater", and I fear that the sentiment is growing so rapidly, as shallow as it may be, that the lack of understanding why America truly is a revolutionary country and is exceptional in history will potent some very turbulent times in the future.
Yes, the system was imperfect from the start, and has been even more imperfect in implementation, but to say then that the whole system (not saying you said this, but it seems thinly veiled to that affect often) must be thrown out is foolhardy at best. The shining light of America is that it has, in it's founding documents, a system designed to self-improve over time. I see our main problem as being the lack of memory of why each piece of that system is so important, and have allowed it to become corrupted. The path forward then is in seeking to enforce the core foundational principles the founders thought very hard about (such as Montesquieu's checks and balances system), and not to discard them just because they came from people that were imperfect.