Advantageous to the minority yes. Not to the others who 'play by the rules'.
I'm sorry but that's nonsense. You know as well as I do that non-union colleagues don't have the option to decline a pay rise. Equally they sacrifice the opportunity to voice their prefered areas for improvements in conditions or any preferences around the size etc of a pay rise. Finally, and to a great many, most importantly, it sacrifices union representation should a dispute with the employer emerge.
Being non-union carries penalties, talking as though such a person is free loading is massively missing the point. There's a great many reasons someone may fall out and disagree with the union and, sometimes, voting with your feet (and wallet), may be the only way to be heard.