There's a commonly-asserted belief around, whereof this (cited disapprovingly at link) is as good a statement as any:
Whether or not your individual ancestors owned slaves, you as a white person have benefitted from slavery and are complicit in it.
Now, this just doesn't make sense to me.
Let's assume, for the sake of argument, that I had ancestors in the Antebellum South*, and that, like most white people, they were not plantation owners. Not being of the wealthy, plantation-owning stratum of society, they wouldn't have been able to afford slaves; they would have been small farmers, doing their own labor, or workers, laboring for the monied classes.
If we assume that slave labor conferred an economic advantage on those who owned the slaves (as seems likely enough, given how long the institution persisted), it follows that those who did not own slaves would have been disadvantaged by it... right?
A family farm without the advantage of slave labor would be competing with the produce of farms that did use slave labor, which one would expect to drive profits down.
A free laborer would be competing against slaves in the labor market, which one would expect to drive wages down.
In both cases, it looks to me like the poor white trash would be getting the short end of the stick... just as citizen labor is put at a disadvantage by the availability of illegal immigrants employed under the table and not subject to the labor laws.
What's more, I know some white people whose families definitely came over long after slavery was outlawed... how, exactly, did they benefit from it?
Looks to me like just another bald (and fundamentally racist) assertion.
* A false assumption, so far as I know, but some branches of the family tree are fairly obscure.