Yes I think it is accurate to say that eventually the white-man will be repressed by their definitions. However I would not be hopeful that this will be acknowledged as an outcome of their system nor would it be acknowledged when it happens. I believe that once the people supporting these views gain the power they seek, then the talk about “oppression” and class struggles will fall away.
As for the why should anyone listen to white men talking about this issue, I am not sure if that is a valid conclusion. The main reason is because I think they allow for the possibility of people in the oppressing class recognizing their position. However this might not work for all forms of post and neo-marxism. Consider, for example, critical race theory. Under critical race theory, being white is something inherently bad. So recognizing and talking about one’s own position as an oppressor would make just as much sense as a slave-owner talking about the immorality of owning slaves, but then not setting them free. A white person cannot abrogate their white-ness, and so cannot give up this evil-ness or position of power inherent within them. So any white person endorsing critical race theory, on their view, would be just as contradictory as a slave-owner believing in the immorality of slavery.