An "impassioned advocate" refers to someone who passionately supports a cause or belief, speaking out about it with great enthusiasm and dedication. Full definition
One result is that the public square is filled by impassioned advocates, while silence reigns among those who may be more versed on the research or more likely to recognize complexities and hard truths. (educationnext.org)
As a persuasive and impassioned advocate of helping homeless animals, Randi became the face of Northeast Animal Shelter. (northeastanimalshelter.org)
The most impassioned advocate I hear from is Mark Henderson, who runs the microwave system that will help heat the plasma. (newscientist.com)