The phrase "outspoken proponent" refers to someone who is very vocal and a strong supporter or advocate of a particular belief, cause, or idea. Full definition
The author is one of the world's most outspoken proponents of a high - fat, low - carbohydrate diet. (paleodiet.com)
In addition, I think our promotion of the use of reason in religion has also contributed to our being at the forefront of equality movements, and outspoken proponents of acceptance. (rachelheldevans.com)
In 37 Signals» case, they have been one of the most outspoken proponents of raising less (or no) VC funding, and keeping your eye on profitability from day one. (businessinsider.com)