Essentially the question posed by these events is:
Are you a moral relativist?
If you are, then you probably agree withe the bombing campaigns, on a "it may have been bad but that doesn't make it wrong" basis
And if you aren't, then the morals of the society become relevant. Most people in Britain and the US at the time supported what was done = it was moral at the time.
We now live in different times.
My personal view is that losing is the bigger immorality to "winning ugly", especially when the other side has a hegemony and/or race extermination policy.