The Apostle writes:
1 Cor 4:3-5
I do not even judge myself. 4 I am not aware of anything against myself, but I am not thereby acquitted. It is the Lord who judges me. 5 Therefore do not pronounce judgment before the time, before the Lord comes, who will bring to light the things now hidden in darkness and will disclose the purposes of the heart. Then each one will receive commendation from God.
Parts of the human psyche are unconscious, and we can’t even know ourselves, much less the heart of another. We can think that we are right before God,but He may see it differently.
Because we cannot know all the things that are hidden in darkness, we cannot judge the persons only their actions. For all we know, he made a good contrition, and left what appears to us as heretical, or at the very least hypocritical, behind.
The roots of it are in the Reformation. But yes, more recently it has become a mandated practice, especially for American Catholics.
Yes, it is fortunate that the Church defines heresy in the CCC. In that same document (link already posted above) the CCC explains why we cannot use this term with others.
No, thanks. I am investing my studies right now in those who were obedient to the Teachings of the Church.
One of my current subjects is Joan of Arc, who suffered at the hands of people like yourself, who felt they were qualified to judge the state of her soul.