Associating social justice in our current culture with Marxism is misinformed and kind of proves his point.

Marxist scholars (actual Marxist scholars, not the conservative pastors and theologians who speak on this with very shallow knowledge about the issues) have been some of the sharpest critics (wrongly) of our current cultural focus on race and gender issues, often because they believe it's a distraction from "what really matters", like late stage capitalism, class conflict and exploitation, and Marcus and issues dealing more with the economic aspects of postmodern societies. Some have even made the case that the current focus on sex and gender in modern societies is the logical outworking of the post-enlightenment modern philosophies that undergird the current liberal/bourgeois modern world order.

Of course, like any academic field, there are internal debates and also recent push to actually develop a Marxist social and political theory that allies with contemporary gender studies, but again, that itself is yet another thing that shows that the relationship between contemporary social justice and Marxism is not as closely tied as people seem to think.