ALF Terrorist?

The Animal Liberation Front was brought up several times and a movie was shown in class about them.  One thing that seemed to shock some of the students and the ALF members was that the ALF was considered the most dangerous terrorist orginization in the United States.  This also surprised me when I heard.  I do think they should be considered terrorists because they do use terror to further their politics.  I do not think they should be ranked the most dangerous terrorists in the United States.  The ALF has not killed anyone and poses little threat to most people.  Surely there must be much more dangerous terrorists in the US rather than a group of radical animal activists.