It is a real bad argument to by the white people to say that "We did not participate in slavery." Because they are participating. They have inheritances from their forefathers, most of which were built through the hard work of the slaves. Nobody gives their money away to strangers, they usually (almost always) give it to their children. White people are passing on wealth from generation to generation whereas black people are handing down poverty from generation to generation.
So, it is really a wrong thing to say on humane as well as reality level, because this is simply not true.
Moreover, the number of black people that die at the hands of police is just alarming. I don't even know whether slavery doesn't exit today. It exists in terms of police exerting their dominion over black people for no reason whatsoever.