So what if everyone choose to get in the SRL, guess what....*GASP*....they can literally only board when there are left over seats and/or odd numbered groups in the main queue. That is how the friggen SRL works! There is no tricky situation. People in the SRL can only board when theres odd numbered/left over seats from the main queue.
The viewpoint of the original poster is wrong and most likely an adolescent who didn't think things through before posting. Kind of like you did.
The only way this is unfair is if the ride/line OP is boarding the train using the SRL prioritized first or even in pairs. For which wouldn't be the guests fault, it would be the ride/line OP.
Also the likelihood that the SRL becomes the majority picked line is unlikely due to there are so many factors with one of the biggest is most people like riding with their family, friends, or people they came to the park with.