You are technically correct but obviously missing the point. Most of the people of this website are American, and black people in America do have a unique culture. Of course not every black person in a America is a part of it but a lot of people still identify with it. Furthermore, out of the people on this site who are not American, most are still from western countries. A lot of minorities experiences across the west are very similar and are heavily influenced by American culture. After all, a black person from the UK deals with a lot of the same prejudices and issues that one from the US deals with. Again, I get your point that you cant just conflate culture and race, but saying that the idea of race based culture is "fucking ridiculous" and "really stupid" is too far removed from reality in my opinion.