pro-lifer vs proponent

pro-lifer and proponent both are nouns.

Word	Noun	Adjective	Verb	Adverb
pro-lifer	Yes	No	No	No
proponent	Yes	No	No	No

As nouns, proponent is a hypernym of pro-lifer; that is, proponent is a word with a broader meaning than pro-lifer:

pro-lifer: an advocate of full legal protection for embryos and fetuses; someone opposed to legalized induced abortion
proponent: a person who pleads for a cause or propounds an idea

Other hypernyms of pro-lifer include advocate, advocator, exponent.

pro-lifer (noun)	proponent (noun)
an advocate of full legal protection for embryos and fetuses; someone opposed to legalized induced abortion	a person who pleads for a cause or propounds an idea