The main purpose of the fifth golden gate stone stele was to develop the disciples' faith in the sect. When it came to matters of what was right and wrong, sometimes it was important to accept the decisions and explanations of the sect over one's personal judgement.
If a disciple couldn't show faith in the sect, then the trial by fire wouldn't begin, and the disciple would be ejected from the fifth stone stele, just like Meng Hao had almost been.
If a disciple could show faith, well... at that point the trial by fire would begin. Then, the level of their cultivation base, as well as their depth of faith in the sect, would determine their ranking.