The problem is that pretty much every employee could be seen to be representing their employer. Even if they do not name the company they work for, the minute somebody else does they become a representative. Israel Folau is an extreme example of this but being fired for legal but unpopular speech is no longer restricted to people with a media profile and I think we need to be honest about that.
I think the comparison with anti-abortion views is actually the best analogy, I can’t imagine calling for someone to be fired from their job because they attended the walk (march?) of little feet and posted a few graphic memes on Facebook.
Telling someone that you think they will burn in hell in the afterlife is not very nice but, as an unbaptised and unmarried mother of two, I am aware that many of the people who post about their religious faith believe that that fate awaits my entire family. I regard their belief in hell as a fairy tale so I’m not bothered by this but I am aware.
The strongest case for the sacking of Folau was that he had already agreed, as part of his contract, that he would not post comments hurtful to gay and lesbian people. On that basis alone, his sacking was clearly legal but it does provide an interesting case for discussing what kind of speech is genuinely unconscionable and why.
To my mind causing sincere offence to others is not sufficient grounds (by itself) for condemning speech since this would preclude a lot of speech that, while hurtful to some people, is part of a broader discussion that has social benefit. I am also not convinced that anyone is entitled to be protected from all speech that is upsetting to them.
Where the line is drawn is unclear but saying ‘according to my religion you will burn in hell in the afterlife’ seems pretty mild. Unless you have already specifically promised your employer that you won’t and had it written into your contract, then again it’s also pretty chilling to imagine other less-lucrative jobs bringing with them employment conditions like that in the future.