The question of them terrorists or soldiers is a rather relative one. They don't meet my definition of soldier, but that is not because of the nature of the attack, rather because of the goal. The Pentagon is a legitimate military target, but the World Trade Center certainly isn't. The WTC was selected only because of the extremely high number of civilian that would be killed, and that marks them as terrorists to me.
As for 'evil', I'm not quite sure what you are asking with this question. I understand that civilian casualties are an unavoidable effect of war. But intentionally targeting civilian populations for destruction is certainly evil. And yes, I consider some the bombing done by the Allies during WWII to be fairly evil, mostly the firebombing Japanese cities. I don't know of any bombing that was done just to cause as many civilian casualties as possible though.
Jay