I am sure your intentions are noble Seagull. But really, as you have observed, it is next to impossible to judge another persons holiness, and if we try, they might do or say something that is super easy to take out of context.
As you have also seen, it is hard enough to judge our own holiness. Instead I try to focus not on “my” holiness, rather I try to judge my own actions. For example, I normally shrug my shoulders when someone cuts me off in traffic. This weekend though, someone cut me off and for some reason this time I started tailgating him a bit in response. It made me mad this time.
Not a holy action. Such actions can result in wrecks and even death. It has happened to people before. I admonished myself and said an act of contrition. Then I parked further away from the entrance out of penance.
By mentioning this though in this thread, according to the gospel I have given up any merits I got by doing this. Why?
"And when you pray, do not be like the hypocrites, for they love to pray standing in the synagogues and on the street corners to be seen by others. Truly I tell you, they have received their reward in full.
I think it is worth it though to illustrate a point. It is a lot easier to focus on someone else than it is on myself, but we are called to do this.
Make every effort to live in peace with everyone and to be holy; without holiness no one will see the Lord.
Everything else is just a distraction. I hope this helps.