Spike Lee doesn’t mince words in “BlacKkKlansman.” He ignites them, and illustrates them with inflammatory images. This is a freewheeling account of an African-American cop who infiltrated the Ku Klux Klan in the early 1970s. It’s uneven as narrative drama, but stunning as a furious, in-your-white-face outcry against racial hatred in America’s past and turbulent present, with pointed references to President Trump.