It was unfortunate, but it was necessary. After what the Germans had done to London, I feel little sympathy, especially given how the death total for the Blitz was higher than the highest estimate of the Dresden Bombings. All in all, although it was a terrible event, it is difficult for me to condemn it too much.
If we are to assume that collective punishment is an acceptable thing and that dreadful things that happen as a result can be justified if less people die in the collective punishment than the initial outrage, isn't as though Dresden was the only city in Germany to be heavily bombed by the Allies and it isn't as though the population of Dresden was close to that of London, let alone the whole of Britain.
I feel I should add that my Grandmother lived in Coventry for much of the early '40's.