As for your last statement, absolutely one can call out someone who is "objectively" holier ... in some respects ... for a "holier-than-thou" attitude. Those Pharisees our Lord rebuked in the famous parable of the Pharisee and the Publican did in fact keep the law much better than the publican, but it's a question of ATTITUDE. All of the saints, who had true holiness, considered themselves to be the least holy of men. That's often been a point of discussion. Was that false humility since it was clearly objectively false, and humility is truth? No, they considered themselves the least holy because they had an acute awareness of their own failings, knew which graces they were offered and didn't live up to perfectly, etc. ... while they granted their neighbor the benefit of the doubt. Perhaps they received fewer actual graces for some reason, perhaps were born into difficult circuмstances, had tendencies from their natural temperament that perhaps inclined them to certain faults, perhaps had tons of circuмstances and prudential considerations and other obstacles that prevented them from living as they should all the time. ONLY GOD can judge souls at that level. We can only judge objective right and wrong.
So, yes, it's perfectly fine, depending on the situation, when motivated by true charity, to point out when people aren't living up the standards of holiness, either to help correct one's neighbor or else to encourage others to avoid those faults.
Why yes, this is certainly what we Catholics should do. However, was that the motivation in the other thread? Was it really about fraternal correction? That certainly wasn't the impression I got. It seemed more like an opportunity to give LT his just desserts, a public lashing, a public gotcha moment as it were. And then someone wasn't happy enough with the other threads: he had to post yet another "αnσnymσus" thread about LT's faults. It seems to me that those folks have a bit of reflection of their own to do.