roy - // How is it abuse if they are lying? //
Because you can't prove that someone is lying, and you have offered no evidence in answer to my post to you about it.
You can believe that someone says something that is not true, but that does not make them a liar.
A Flat Earther is not a liar, they are simply saying something that is not true. However, they believe it to be true, so they are not, in fact, a liar.
And it's not nice to be abusive to someone based on something you believe, so best not to pursue that point in my view.