Double Naught Spy,
There's no point in debating the semantics of the phrase "terrorist act", or how much ground its umbrella covers. I'm familiar with what it is and what it isn't. The Wiki version is nice, but there's more to it than that.
This is your quote:
Actually, it is motivation that is the distinguishing difference between a terrorist attack and mass murder or serial killing. Unless the attack is carried out against civilian targets for the purpose of bringing about social, political, or religious change, they are not terrorist attacks.
Harris and Klebold attacked a segment of a civilian population who they believed had wronged them with the purpose of intimidating that population, creating fear, and bringing about social change. Are they the classic terrorists that we all think about...Hamas, Hezbollah, IRA, al-Qaeda? Nope. Do they meet the definition (which is one of over 100 definition, by the way)? Yep.
But since you read my post so carefully before pulling the trigger, you surely noticed that I didn't equate the typical motivation(s) of the different groups in the first place, but simply pointed out that their methods were similar in some ways. Go sharpshoot somewhere else.