Some of the comments in the DM article illustrate a part, at least, of the problem. Dresden is compared to Coventry, London (and you could also include Hull, Bristol etc etc) as if Dresden were the only city we bombed heavily. But it wasn't. We also bombed Nuremburg, Koln, Hamburg, Frankfurt, Dusseldorf, and every other major city. The results were devastating.
This is not to condemn one as worse than the other, although our bombing raids were certainly larger, more sustained, heavier, and more fatal than anything the Luftwaffe managed. Does that make it worse? Objectively, perhaps. The key differences are that a) we won, and history is generally favourable to the victors, and b) to start with, at least, there can be no doubt that the Germans were the main aggressors. As long as we were under direct threat, we probably had to cross the line in order to protect ourselves and win the War. Indeed, if the Germans had landed on our shores and invaded, we probably would have, and certainly should have, thrown gas at them for all I care.
Perhaps, with hindsight, things can be seen to have shifted some time between about 1941 and 1943, when we went from defending ourselves to being the aggressors, and that does make the civilian bombing later in the War more questionable. It's also a bit one-sided to portray only the Nazis as War criminals, although again this was almost inevitable once they lost and there is no doubt that many of them were guilty of War crimes.
I don't think it lessens our appreciation of the bravery of those who fought for us, not even of the Bomber crews, to question what they did. We should question it. We have to, in order in part to make sure that, indeed, it never happens again.