“The word in the article, “truthism” is made up by the author to create an insult, a nonexistent condition and something that the author says he hates. It is not in any standard dictionary. It is not a commonly used or recognized word. It is not by any definition a real word.”
Ah, you see there is where you’re mistaken. The author did not invent the word “trutherism”. That word (and its variations, like “truther”) have indeed been in common usage for years now, as a simple google search can verify. It may be insulting to those who don’t like being described by it, but that is immaterial, since there are countless words in the dictionary that were invented as a derogatory label, which are all “real” words, under your definition.
A small group of people that questioned the 9/11 attacks referred to themselves as the Truth Movement. Some people referred to this small group as “truthers”. It became a lazy and dishonest slang among a very small number of people to refer to anyone who questioned any of the official explanations of 9/11 as “thuthers”. That is what you are referring to. Normal people do not use the word. It is used dishonestly by a very small number of people.
The word was used dishonestly. It had no meaning. It meant whatever the user wanted it to mean.
Now this author makes up the word trutherism which he says he “really hates” to describe something that has nothing to do with 9/11.
It is a made up word. It means whatever the author wants it to mean. It is not in a standard dictionary. It has no common usage or commonly accepted meaning.