Some of them are probably liars, but I think that most of them are simply, well, stupid.
I'd be willing to bet that the TSO whom KDS referenced in the OP truly believed that it was always the policy that shoes had to go in the bin by themselves, but that some TSOs were simply doing it wrong all along.
Rather than clarifying the apparently discontinuity with her superiors, she simply proceded on her merry way, telling pax that shoes must be in a bin by themselves, because she was so sure she was right, nothing could disuade her.
Obviously, anything that a traveler tells a TSO cannot be acknowledged as right, because if a TSO acceeds to a traveler's request or demand, or accepts what a traveler tells them as being more correct than what they already knew, then they are handing over some measure of power to the traveler. And, just like most LEOs today, TSOs seem to be either trained or pre-disposed to always maintain complete, iron control of any situation and any person with whom they interract on the job, and will use whatever means they have at their disposal to maintain that control, including punative searches and interrogations, denial of flight, and even false accusations designed to have a traveler arrested.