The pugilistic US Representative (R-Ohio) does not wear a jacket to public hearings. When asked if he ever wears a jacket, he said that when he needs to show respect (e.g. a visit to meet President Trump) he does wear one. By implication, this means that being invited to attend the Impeachment Hearing is not sufficient reason to show respect. A possible slight to his colleagues and/or to the American people? Judge for yourself.
It is difficult when sparring with an adversary, during a mediation session, to show civility and even respect. But at what price? Being ornery is a self-defeating stance. If you have self-respect, you can manifest this by showing respect to others. This applies equally to those with whom you disagree. Is wearing a jacket while representing the good people from the Buckeye state really too much of a sacrifice? Civility is always in fashion.
Mediate don’t litigate.