so it is OK for any organisation to sack an employee for expressing their Christian beliefs?
No, that is absolutely not what happened.
Firstly, do you think that every statement in the name of a religion is exactly the same? Clearly they are not. Folau has made dozens of posts that have caused absolutely no issue because they don't vilify others.
There has been no attempt to stop players observing their religion and making religious posts on social media. There is a prayer circle after half the games now. It is very common place.
There is always a line between appropriate behaviour and inappropriate behaviour and Folau crossed it. Just because it is to do with his religion doesn't mean that there is no line and he can carte blanche say what he wants without repercussions.
He was then given many roads back to reconcile with RA and move on from the situation without his contract being terminated. He refused to engage at every point.
Trying to paint this as Folau quoting the bible on social media and getting fired for it leaves out so many pertinent details that it barely scratches the surface of what led to the termination of his contract. It's convenient though when you're trying to argue that this is an attack on his free speech.