Habeus Corpus for TERRORISTS

Why is it so hard for people to get their heads around the idea that even people accused of being terrorists are INNOCENT UNTIL PROVEN GUILTY. At any time, someone can accuse you of something terrible, say child molestation, but the government is required to treat you as though it is not true until proven otherwise. They can't lock you up, assume it is true, and never give you a chance to defend yourself against the accusation. Why is terrorism different?