This seems to be about the best definition I find.
Terrorism
In the international community, terrorism has no legally binding, criminal law definition. Common definitions of terrorism refer only to those violent acts that are intended to create fear (terror); are perpetrated for a religious, political, or ideological goal; and deliberately target or disregard the safety of non-combatants (e.g., neutral military personnel or civilians).
Reference:
http://en.wikipedia.org/wiki/Terrorism
Terrorism has been active in this country before the term was popular. The KKK is not, was not the only group who have committed acts of terror in our history. We have had plenty of strikes and riots and violent protest.
Or does the fact some think it was/is a worthy cause make it not terrorism?