Terrorism is, in fact, no different. It doesn't require a war. To declare "war" on terrorism is to admit a permanent and perpetual state of war. A state wherein abdication of human rights and constitutional rights can be falsely justified and facistically implemented. Not to mention all other the other horrors and economic siphoning that would be a permanent state of being with a permanent state of war.
If we treat terrorism as the crime that it is, we can fight it just as we would any other heinous crime, and battle organizations that commit terrorism the same as we would any other criminal organization.
The danger to our society from terrorism has been insignificant compared to others we are not throwing treasure at. A war is not an appropriate economic or moral response to acts of terrorism commited by ad hoc organizations. Where is the "war" on the mafia? Where is the "war" on the bloods and crips? Far more Americans lie dead or wounded via the acts of these criminal organizations than from those of international terrorists (though I'll grant that terrorism adversely affects our economy to a greater degree with far fewer and less lethal acts of violence).
Risk assessment would be prudent to apply to international terrorism.
And yes, it would be wonderful to rid the world of all despots and evils. Would that we could. And if we could, would war be the proper way to rid the world of evil?