i guess if they did it with the intent of modifying and changing the behavior of others through intimidation, threats, destruction of property etc, then its terrorism.
to them, its just a "cause" to make them feel good about themselves... and they are always led by older, predatory morons who prey on lost and wayward kids searching for the meaning of life, usually after getting kicked out of their parents house for smoking dope.
*yawn*
if i was there, i would have shot them to protect my cars.