hard line vs stance

hard line and stance both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard line	Yes	No	No	No
stance	Yes	No	No	No

As nouns, stance is a hypernym of hard line; that is, stance is a word with a broader meaning than hard line:

Other hypernyms of hard line include position, posture.

hard line (noun)	stance (noun)
a firm and uncompromising stance or position	standing posture
	a rationalized mental attitude