You see, that's the clever part. Make sure there is some verisimilitude and you can't go wrong.
"For the reasons given I am satisfied at least on the balance of probabilities that Mr Mitchell did speak the words alleged or something so close to them as to amount to the same including the politically toxic word 'pleb'." which is all that is needed in these cases.
This should never have got this far but nobody comes out of it with a clean record. Someone leaked this alleged exchange and fabricated elements of the story, such as members of the public being present and being 'visibly shocked'.