Aside from the final bit of general - I refuse to engage with someone who doesn't share my viewpoint (a fairly standard trick in online discussions) this is actually a reasonable argument.
Unfortunately, it does litlte more than support the argument that I've made. Everyone has their own lived experience and systemic racism is definitely a thing - but ironing out the nuances does little to resolve the problem.
In this instance, your great grandmother is likely a lost cause. The racism she has was likely formed in a world where black vs white was the norm. She would've been fed false dehumanising information about black people, and she's unlikely to have the psychological will or brain plasticitiy to change these views. Her opinion is her opinion and that is that.
But now consider someone who is seven and belongs to a poor white family. Do you think the arguments being presented about white and black people as collective homogenous groups are likely to cause their parents to be more or less racist? Particularly in the absence of any black people in their immediate social circle. The argument that ALL black people are subjugated by ALL white people is more complicated in the modern age when you consider the intersection of class.
Put simply, middle class black people insisting they are more oppressed than dirt poor white people will lead to more people like your great-grandmother in the fullness of time. The argument works well in metropolitan liberal cities but not well across broader swathes of the population. If you're interested in unpacking this further, I wrote about it here.
