Modern technology allows for precision that was impossible in WW2. Using civilian casualties in WW2 to justify them today is horrible.
WW2 was a total war. This isn't even a war according to our laws. Even if we concluded that the firebombing was acceptable (and oodles of people call it a war crime), this does not transfer that justification to these attacks.
I am also not terribly interested in using the evil acts of terrorist groups to justify our own evil acts. Would it be acceptable in your mind to behead captured Iranian PoWs because various terrorist groups do this? I would hope not.
