No I don't think the hammonds are terrorists they were convicted of arson, I've not seen them called that either.
It has to do with the Federal statues they were convicted under having the word "terrorism" in them. Folks that do not read regulations pick up on select words and then cast a broad screed with no fundamental understanding of anything. The only people using the word "terrorist" or "terrorism" are the protesters.
Here is a link containing two press releases about the case. A jury of their peers convicted them, not the Feds. Why do people loose sight of that.