apologist:
(plural: ‘apologists‘; pronunciation: the letter ‘g’ is said with a ‘j’ sound as in “judge”)

Apologist Ben Sheriff of Layman's Logic
a person who argues in support of some belief or opinion or defends a belief or opinion by loud argument;
(old usage) any of early Christian writers who defended Christianity and wrote and recommended the word of Christ (in this context, an ‘apologist’ is also called ‘apologete‘),

John Blanchard, Preacher/apologist
In modern times, the word ‘apologist’ refers to any writer, editor of science or academic journals and political leaders known for defending (arguing in support of) points in issues of conflicts.
Martin Luther King, Sr., the father of Christian reformation, was the greatest ‘apologist’ for Protestantism of his time. (from Answers.com/Wikianswers)
