Of course, institutionalized racism is the short answer. The long answer begins: A word or phrase is only a placeholder for mental images. Depending on a persons level of education and intellectual capability, the word "black", for instance, when used as a racial identifier, conjures the imagery of over 500 years of racist oppression.
From the perspective of historical discourse,when we ask ,"Why the oppression?" We are forced to state the obvious, "Because millions of Africans were forced into slavery here in America, and the majority of them happened to be dark skinned, or "black". Or if we start a conversation with, " Who was oppressed and forced into slavery?" We are also forced to say, "The African" , or "blacks".
From a modern perspective, it would be difficult to discuss any issue concerning racial discrimination without using some kind of an identifier. The phrase, "The group is targeting and discriminating against men", is a very broad brush that tells us very little. However, the phrase, "The white supremacist group is targeting and discriminating against black men", gives us a more detailed image.
As long as institutionalized racism continues in America, there will be a need for racial identifiers. But I suggest that the use of "black" and "white" should be discontinued in favor of "European" and "African": This is important, because there is a rich European and African history that has continued for thousands of years, whereas, "white" and "black", as understood today, only exist from 1492 forward. Furthermore, these hollow terms only remind, and conjure images of oppression, rather than cultural diversity, ancient technology, and great works of art.
The above sentence more properly spoken is as follows: "The Euro-American supremacist group is targeting and discriminating against African men". It is important to note that I used "African" in my phrase rather than "African American", since to the educated mind, to identify the African as a member of the oppressive group that enslaved them is insulting and demeaning. Just as it would be to identify Jews with Nazis.
Finally, you will notice that my profile picture is blue. Since I am ahead of the curve, I understand that my people, the so-called "red man" is now the color blue. The color symbolizes death, because America has attempted to turn even the living, the few of us that remain, into ghosts.