Why wasn’t he allowed to say it?
I'm not sure I have this correct but in an earlier trial he and others were found guilty (regretfully the jury said) of criminal obstruction for gluing themselves to a train.
In that case the same judge told the jury that the defense of necessity could not be used and instructed them to focus on the accused actions not their intentions.
This is a rerun of that scenario where the judge said that intentions were not relevant and should not be referred to. Mr Nixon ignored him, the jury were sent out and he was given 2 chances to apologise.
He chose not to and was found in contempt.
That is how I understand it and pass no judgement whether it is right or wrong. You can sympathise with Mr Nixons stance and his integrity in not apologising yet if a judge tells you something is inadmissible and you ignore it then it's contempt.
PS the comments about the judiciary and the tories above in respect of this case are b***ks.