I didn't know a great deal about Powell until about a year ago, and although I knew I didn't like his politics, I still was willing to think of him as not being all that bad, more like a 1960s UKIP than, say, the BNP. But the more I have studied him and his career, the more I've become convinced that even if he might not have been a 'racialist' in the sense he didn't believe in the genetic inferiority of races, he was nevertheless a blatant racist.
Although 'Rivers of Blood' is cleverly crafted so that Powell can present himself as the 'honest prophet' who doesn't agree with the sentiment that is being expressed but feels duty bound to report it, I don't see how anyone could conclude anything other than that his sympathy is pretty much entirely with the whites who are expressing racist views- particularly in the passage about the lady who won't allow black lodgers in her house. He was pretty blatantly pandering to prejudice and bigotry in that speech, and I think that was precisely what he had in mind when he was writing it.
Although he was careful not to say much himself which could be construed as 'racialist' he never disavowed his supporters who did express that kind of sentiment. If you haven't seen this
documentary already, I would strongly encourage you to do so, he seems to if anything be proud of the letters of support he has received from members of the public who clearly harbour racist views. At one point, the interviewer puts it to him that he is a racist, and he responds by saying "what's wrong with racism?" Which is a pretty damning indictment of his world view.
Plus he did call for a large scale program of repatriation, which is an idea that is straight out of the playbook of the NF and the BNP. Powell wasn't the fascist some make him out to be, and he probably wasn't a racialist either, but he nevertheless held some pretty distasteful views to say the least, and a world where he became PM would be a pretty dark one.