They are not stupid, but I would not call it reasoning.

I suppose they have made some bizarre extrapolation, like: "If he will not be going to the inauguration, that is because he refuses to concede the election, in which he was clearly defeated, and which was clearly fair. This is the latest example of what an unreasonable man he is, and how he cares only about himself. He is flouting (being 'violent' towards) our democracy. Therefore, his statement is a dog-whistle to his extremist support base to come to Washington and commit 'violence.'"