In boxing circles, by saying someone's not a "boxing purist" is more or less knocking their lack of knowledge of the sport as a whole rather than combining the literal meaning of the word purist with boxing. I've seen many definitions of "boxing purist" but the best I've come across is this.
A Boxing Purist is a person that appreciates the true beauty of the sport....feels, loves and understands the profound nature of the Original Gladiator Sport...A boxing purist admires the courage it takes just to get in the ring and face another man with the same goal and/or objective...A boxing purist can "hate" a certain boxer but respect him at the same time....A boxing purist has a certain affection for many ring styles and understand's the cliche that "style's make fights"...They most certainly do!! A boxing purist will watch almost any boxing match just because "you never know" where you'll find a great match...more times than not the great fights are NOT the ppv "hype fights". A boxing purist can see the HUMILITY in a man like Mike Tyson inspite of his short comings and disappointments...love him or hate him is legacy will live far beyond our years on this earth...A boxing purist begs for a fighter to retire for fear of seeing that boxer get hurt....even if it's just "one last hoorah"....
Oh, and a boxing purist usually doesn't like watching boxing in loud distracting places...purists like to hear the fight, the commentary, the crowd reactions, the cornermen, the impact of the punches etc...
I've seen some other very good definitions of a "boxing purist" and alot of them aren't true to the dictionary definition of purist.