I've never called anyone a liar without having facts to back up my assertion. For example, if someone says I have never addressed a point of contention, and I know I have addressed that point of contention, and I know the other guy knows this, the only conclusion I can draw is that the other fellow is lying through his teeth. As for mental illness, I certainly am a bit eccentric (my major goal in life is to be an eccentric old man), but nothing that would excuse my actions in a court of law.
So far, I've never really seen anything on these threads which would make me want to call anybody a liar. It used to be that calling somebody a liar was always good for starting fights and anybody who used words like that loosely, as you appear to, was somebody in a permanent state of getting his ass kicked in. That may be something which has changed or a symptom of some sort of a generation gap, but it still sort of throws me for a loop to see anybody using language like that loosely.