Heather Mac Donald writes at the always excellent City Journal:

Since last summer, a lie has overtaken significant parts of the country, resulting in growing mass hysteria. That lie holds that the police pose a mortal threat to black Americans-indeed that the police are the greatest threat facing black Americans today. Several subsidiary untruths buttress that central myth: that the criminal-justice system is biased against blacks; that the black underclass doesn't exist; and that crime rates are comparable between blacks and whites-leaving disproportionate police action in minority neighborhoods unexplained without reference to racism. The poisonous effect of those lies has now manifested itself in the cold-blooded assassination of two NYPD officers.