Loras' trial on tonight's Game of Thrones ("The Winds of Winter") was over before it started. He took it upon himself to confess before the Faith could drag him through the mud, but while it might have saved his life in the moment, it lost him everything else. He gave up his name, his title, his home, and his future. But why did Loras denounce the Tyrell name on Game of Thrones?
Loras did it to save himself, even if it ended up being all for naught. Confessing to his "sins" and renouncing his birthright meant that Loras was shown mercy, or at least the Faith's version of it. That mercy still came with its fair share of bloodshed. Loras agreed to join the Faith in upholding the religion of the Seven in whatever way they required; though this would have allowed him to live, it still resulted in Loras being held down while the symbol of the Faith was carved into his forehead. Margaery and her father were horrified, but the High Sparrow promised her that after that Loras would be allowed to go if he wanted to.
Unfortunately, none of it mattered. Cersei saw to that.
Cersei used wildfire to blow up the Sept of Baelor and everyone in it, Tyrells and Sparrows alike. Margaery knew something was going to go down when Cersei didn't show for the trial, but she had no way of knowing just what. Though she tried to save everyone in the sept by pushing them to the exits, the Faith stupidly prevented everyone from leaving so when it was blown up, Margaery and Loras were caught in the blaze. R.I.P.
It's incredibly tragic that Loras' last months were filled with suffering, and his last moments filled with pain. When he first appeared on the show, he was the very picture of a chivalrous knight: nice armor, flowing hair, and some serious skills with a sword. The Knight of Flowers was charmingly arrogant and prepared to help those he loved come to power, pushing Renly to take the throne from his brother Robert and even marrying Renly into his family by hooking him up with Margaery. Loras was vain and a little power-hungry but hardly the worst Westeros had to offer and in the end, he was truly a victim. His only sin in the eyes of the Faith was his sexuality, and that isn't a sin at all.
Loras didn't deserve the hand fate dealt him, but that's often the way things go on Game of Thrones.