Judges, JPs, sheriffs (in Scotland), anyone presiding over a court, may not subject the other participants to interruptions, or to a level of testy temper that is not allowed to be shown back to them.
Everyone who is speaking shall be entitled to finish the sentence, and if they are in mid-explanation, to finish the explanation. The relevance of any explanation to the case may only be judged after it has been given and completed, not in an interruption made when it is still in progress.
It shalle never be contempt of court to stand up to browbeating, impatience, testiness, snapping, from the judge, by yourself treating the judge in exactly the same equal way in return. Thus shall the argument be kept fair.
Why is this idea important?
Any authority figure allowed to be testier than can be done back to them, can browbeat and bully. this applies to school teachers too. If a judge stops what you are saying in mid stream, you don't get your point across, hence what you have said is left distorted. It is shattering to your confidence and your emotional state, hence to your ability to cope and not to be overwhelmed unfairly by the trained pro who is questioning you for the other side. The cases content can be distorted or censored.
For any authority figure to have this discretionary power allows corrupt mainopulation or falsification of the case. it is a relic of the Middole Ages.