A simple check of the dictionary points out the fallacy of the common usage. One of the definitions is “a person who is expert at his or her work.” Another references “a vocation requiring knowledge of…learning or science.” Nowhere in these admittedly selective definitions is there a mention of financial compensation.
Professionalism isn’t about pay, it’s about attitude. It’s about your approach to a job. There are volunteers who join departments for all the wrong reasons and there are career personnel for whom the job is nothing but a paycheck. However, there are many truly professional firefighters, officers, and chiefs in the volunteer ranks which should be recognized as such.