People use incorrect words to categorize those they do not like. They use string words such as "liars" or "n-word" or "stupid" etc.
I do not believe that individual Jehovah's Witnesses, Seventh Day Adventist, Mormons, Catholics, Lutherans, Baptists, etc are purposefully lying? I believe that they are in ERROR.
Lying is too strong a word (and an incorrect word) to use to categorize the things "individuals" of the various religious groups teach and repeat. This is especially so in a world The Apostle John says is under the power of the wicked one. It is the wicked one who dispenses the lies in the air. These lies permeate and infest everything, especially religious organization.
The lie is simply taught, the people accept the lie as truth and light, and they repeat it.
Thus people are in error. Why? Because they do not know. Christianity claims it knows. It does not know either. Only Christ knows as he is our Teacher. (Luke 9:35)
Easily calling other liars is not thinking as one should. If one knows one is in error, then this prevents condemning anyone. Something Jesus never did.
Sadly, too many persons let the drug of "emotion" cloud their thinking. Thus, it is easier to think people are lying rather than being in error.
Did not Jesus forgive the error of his persecutors and executioners because they "did not know what they were doing?"
If one does not know then they are not liars, they are in error.