That statement, as it stands, is ambiguous, and that its implications depend a lot on what it's taken to mean.
Statement 1: Many of the people involved in the decay of Detroit were black.
Statement 2: Many of the people involved in the decay of Detroit were black, and their blackness was an important factor in the decay.
Statement 3: Many of the people involved in the decay of Detroit were black, and their blackness was an important factor in the decay because of some actual difference between black people and white people.
Statement 4: Many of the people involved in the decay of Detroit were black, and their blackness was an important factor in the decay because black people are stupider or nastier or crazier than white people.
Statement 1 is clearly true. Statement 2 is not clearly true. Statement 3 is very likely false. Statement 4 is almost certainly false. (These are of course all my own opinions; I am not claiming that they are self-evident.)
Statement 4, if true, might well have implications like "We should try to get rid of the black people" or "We should make it easy for white people to keep black people away from them" or "Black and white people should be segregated". Statement 1, on its own, would not.
There are plenty of people around who would endorse something like statement 4, and who would be happy to draw such conclusions. It is widely considered (and I agree) that these are not very nice people, and that the policies they prefer would be socially harmful, and that many of the things they believe about black people are factually wrong, and that if their ideas were more widely believed it would be a very bad thing.
That is why expressing views like statement 4 may "get you shunned". For the same reason, if what you intend is (say) only statement 1 then it seems to me that you ought to make that clear.
(I must say that I don't see why anyone would find statement 1 interesting, unless they think that what's really true is one of those later statements. And if someone finds such statements worth making, I am going to suspect that they may have in mind some conclusions of the sort I mentioned above. I suspect I'm not alone in this.)