Every example you mention is basically military commanders handing out summary executions for traitors, outlaws, or deserters during wartime. That wouldn’t be unusual even in our modern day, and it’s certainly not comparable to the type of criminal prosecutions that the High Sparrow is undertaking.
“The trials conducted by the elites had preordained outcomes for people who were not guilty of the crimes they were accused of.”
Certainly they have tried to rig trials in their favor, no doubt, but in every case, the accused still received a trial, had the opportunity to speak in their defense, call witnesses, and failing all else, appeal to trial by combat to receive a fairer outcome. The High Sparrow has systematically eliminated all of those options for his prisoners. So if you think the trials conducted by the elites were unjust, unless you say the conduct of the High Sparrow is even more unjust, you’re being hypocritical.
“The people who were to be tried by the Sparrow were guilty of the crimes they were charged with.”
So what? Guilty people don’t deserve legal protections?
You continue to view this through the prism of contemporary Western culture instead of the Westerosi prism. They are not the same.
There is obviously no presumption of innocence, no juries, no lawyers, no appeals, civil rights and apparently few legal protections for the accused.
Loras and Margaery were allowed to go free after they admitted their crimes. Cersei was allowed to go home to await trial for regicide after she admitted incest with Lancel. These were certainly better outcomes than what Ned and Tyrion received.