Guerrilla warfare is defined as "the use of hit-and-run tactics by small, mobile groups of irregular forces operating in territory controlled by a hostile, regular force" and has traditionally been used about smaller groups of foot soldiers, like the ones led by Che Guevara.
Guerrilla warfare =/= Terrorism. There is a difference.
Both are killing to achieve a means. I suppose that fire bombing women and children is also a nice clean sanitary way of war, as long as it is properly done by nice uniformed heroes flying shiny airplanes - as opposed to killing them with a bomb in a baby buggy. They are just as dead.
Therefore, I don't think that an airborne attack can correctly be called guerrilla warfare.
I don't think he is saying that. He is saying that terrorism is a means to an end, just like bombing raids. As I pointed out, historically terrorist attacks have many less civilian casualties than bombing raids. (Compare 9/11 to Hiroshima. Keep in mind that the majority of those killed in Hiroshima were neither IJN not IJA personel.)
Before people make statements regarding terrorism they need to understand how war between nation-states works. I mean the gritty details.
1- War of maneuver between armies. Army A finds Army B on the field of battle and beats them. The war is decided by the outcome of a battle. Napoleonic Wars.
2- Industrial Warfare - People don't kill people, bullets do. People soak up bullets but they are an expendable resource. Basically, you throw as many bullets as you can at the other side to wear out their industrial production. WWI.
3- Blitzkreig/Shock and Awe. You maneuver your armies so fast utilizing combined arms that you overpower their forces at one spot and are already in their hinterland threatening the base of their production before their armies are even geared up to fight. WWII in France, Denmark, Poland, Netherlands, etc.
3a - Just use bombers. Either way, the point it so bypass fighting and hit their industrial capabilities with minimal loss to your own forces - i.e. men are no longer bullet sponges, just kill the factories (and whoever gets in the way. Bombing campaigns in Germany and Japan. We tried to do the same in VN.
4- 4th Generation Warfare is all about ROI. Do as much infrastructure damage as you can for the least cost incurred by the aggressor. You can continue using planes but precision drones do the same thing. Cyberwarfare is another alternative. They use computers for command and control - kill the computers. Likewise, terrorist attacks can be used to sap the will of the people or better yet - cause systemic damage to their networks (electrical grids, transportation, food supply, water supply, commerce, etc.).
Terrorism allows NGO (non-govt. organizations) to carry out systemic damages in the same way that bombing campaigns could for a regular government.