Why would it be contempt of court? She's neither a witness nor a defendant, or commenting on a trial in progress, or defying any court order.
People really can say what they think. They should say what they think and we should support their right to do this, if we also want this freedom. If Maggie Chapman disagrees with the law, she's every right to organise to change it. What she hasn't the right to do is break the law that exists.
Similarly, if the Labour party don't now agree with the Equality Act they themselves enacted, they can legislate to change it. They have a majority and could do this tomorrow. This is how our system works. What they can't do is ignore the law of the land.