Both Uses

advocate
in
The Narrative of the Life of Frederick Douglass
(Edited)

He who sells my sister, for purposes of prostitution, stands forth as the pious advocate of purity.
Chpt Appe

advocate = public supporter
He who is the religious advocate of marriage robs whole millions of its sacred influence, and leaves them to the ravages of wholesale pollution.
Chpt Appe *

Definitions:

(1) (advocate as in: to advocate)
to recommend or publicly support (someone or something)
(2) (advocate as in: an advocate supporting)
a person who publicly supports and works to advance a cause

or more rarely:

someone acting in the role of a defense lawyer in England's past and in some jurisdictions today
(3) (advocate as in: an advocate in court)
a lawyer or officer of the court in some jurisdictions in Europe, colonial America, and the military
(4) (devil's advocate as in: I'll play the devil's advocate)
a person who takes an unpopular position to encourage debate or test ideas
(5) (meaning too rare to warrant focus)