As we know all humans are liars. Except perhaps for those few on the strong autism spectrum like Aspergers that find it nearly impossible to recognize lies nor to knowingly tell lies.
So when folks speak about others lying, they might also try to recall the whoppers they themselves spurt from time to time. There are varying types of liars. There are many things that help define a human being, and one is lying.
Just look at the articles, and the comments here on this platform.