As a Historian, Cooper is supposed to comment on factual information. On the facts, he’s correct. The RAF began bombing German cities on the 16th of April 1939. The German Blitz of Britain did not begin until well over a year later.
“The RAF began bombing German cities on the 16th of April 1939”
Before WW2 started? I don’t think so. The Germans bombed Rotterdam, killing some 800 well before the Brits attempted to bomb Germany