I agree that we should not judge the decision to advance III Corps based on murder trials, embezzlement, or bearing false witness against others, etc.
There were thousands of reasons Sickles advance was unfortunate. Specifically how disruptive it was to the AOP's defense and the number of troops moved or disrupted to rectify the mistake. Burling's Brigade was divided and mixed in here and there and intermixed commands seemed to factor negatively at the Peach Orchard, Carr was borrowed from, Tilton and Sweitzer (effective or not) were advanced when they could otherwise have been in reserve, Caldwell's Division got consumed, Willard's Brigade was called from the area of Ziegler's Woods towards the Cordori Thicket, the 1st Minnesota had to nearly sacrifice itself and the bulk of the XII Corps, save one Brigade, left Culp's Hill. I'd respectfully submit that the high water mark of the Confederacy may have been it's occupation of lower Culp's Hill which was handed to them because of events Sickles put in motion. Had the sun been up longer, the Baltimore Pike was there for the taking which likely makes Cemetery Hill untenable. Overall, the move forced the AOP to assume the tactical offensive when they were in a defensive position causing unnecessary casualties. Just my humble opinion.