Long sword could mean a one-handed sword with a long blade, or it could mean a two-handed sword. I suspect the latter would be the more common meaning.
Two-handed swords were at the time still used as home defence weapons and to take on crowds of people, so that would make sense in context.
How do you know but ev'ry Bird that cuts the airy way,
Is an immense world of delight, clos'd by your senses five?