So basically you're asking if hate-crimes intended to scare immigrants qualify as terrorist attacks?
I think there's a reasonable argument to make that yes, they could be considered terror attacks. Much like abortion-clinic bombings/arson.
-civilian targets
-political motivation
-intended to intimidate others into a course of action.
Of course, like abortion clinic bombings, most people won't actually call this terrorism, because as far as they're concerned it's only terrorism if there's Muslims involved.
-k