I find it somewhat odd that anyone would dispute that Arthur Harris held colonialist views. In his time we had an Empire! An Empire to which Harris gladly contributed to maintenance and expansion of. There's little question of him being an ardent supporter of the British Empire.
I am not going to go into the ethics of toppling statues, or whether any individual does or does not deserve one, it's not a debate that I'm interested in. Discussions of Harris raise some interesting points on ethics, Airpower and RAF History though.
In the 1920s Italian theorist Giulio Douhet wrote The Command of the Air, a classic text on air power that laid the foundations for strategic bombing. Overlapping with interwar ideas on "Total War" and the increasing role of civilian efforts and morale in warfare, Douhet argued that in future conflicts air power ought to be used to bomb the enemy's cities and civilian targets. Douhet openly wrote that his intention was for airpower to be used to cause such misery and suffering that the enemy population would rise up and demand that the state and the military end the war. In essence, Terror bombing.
During the interwar period Douhet's particularly brutal school of thought was influential. It's known that the Germans took an interest, as did Curtis LeMay and others in the USAAF, and more significantly Sr Hugh Trenchard, Sir John Salmond and Arthur "Bomber" Harris. These ideas were instrumental in the RAF's Air Policing of Iraq. After a round of defence cuts (an eternal problem it seems) the government of the day asked Trenchard for a cheaper option to control Britain's new imperial mandate in Mesopotamia. The solution the RAF arrived at was "Air policing", a policy which Air CommodoreLionel Charlton (who later resigned over the matter) described as using aerial bombs as a substitute for police truncheons. Crushing insurrection with the indiscriminate use of aerial bombs and poison gas against civilian homes. After an incident in which British aircraft reportedly machine gunned women and children, Churchill himself protested to the Chief of Air Staff over the brutality of these methods and called for the court martial of those responsible. This was decidedly not the RAF's finest hour.
Harris, as a squadron leader saw firsthand and participated in the Iraq air campaign. He was not it's architect, but nevertheless he was enthusiastic participant in one of the darker chapters of British Colonialism. In that sense if he were described as a "Colonail Warmonger" to me I'd find it hard to say that it was untrue. His wartime actions though are perhaps more complicated. As the commander of Bomber Command, Harris applied Douhet's ideas against Germany, effectively hoping to prove Douhet correct, that Germany's will to fight could be undermined by the destruction of cities, and that his bomber fleets could end the war on their own. To those who condemn the use of Douhet's "Total War" methods which indiscriminately target German civilian and soldier alike in Dresden (or later the use of the Bomb on Japanese cities) the reply is usually that the allies acted only to end the war, and that the ends - the liberation of Europe and the end of the war in the Far East - justified the means. Nevertheless the killing of civilians as an end in itself during the war is a crime that we more often associate with the Germans, and it is uncomfortable to think that this was essentially the RAF's strategy..
None of this diminishes in any way the heroic acts of allied airmen, or of the Bomber Command crews Harris commanded. Like any historical figure though he was complex, and as hard as it is we do have to reconcile with the fact that the Arthur Harris who was the hero of Bomber Command is the same Arthur Harris who was instrumental in the "Air Policing" in Iraq and the destruction of Dresden.