This particular sentence is not entirely correct, as it implies that freedom fighters can’t use terror tactics and thus be terrorists.
Say, if some Armenian force (there are none that’d have the balls) would bomb the Mingechaur dam, the pipes and infrastructure going through Tovuz, other smaller hydroelectric objects etc in Azerbaijan, - these would be actions aimed at fighting for freedom, but very important part of their effect would be terror.
In some way any violent activity aimed at denying someone their feeling of safety is terrorism. Like, say, allied bombing campaign of Germany (its goals were even formulated like that).
I agree that Hamas are not freedom fighters, their ideology is pretty Nazi.