the mind > attention and judgement > testing > debate, disputation, argument > putting forward for discussion > [noun] > defensive argument > exponent of (3)
A person who upholds or supports something in speech or argument; a person who contends for the truth or validity of a doctrine, assertion…
One who apologizes for, or defends by argument; a professed literary champion.
One who apologizes (in modern usage for a fault or offence; in early use = apologist, n.).