@PickAChew
t cannot be a free for all. If Norman held a firm belief that all women should stay at home to the point that he would refuse to work alongside a woman, whatever her role, you would not pander to that belief by sacking women or giving their tasks to men.
If Dave held the opinion that BAME people were evil so strongly that he refused to serve them in your shop you would want to be able to take action against him for not doing his job properly without him being able to claim that his was a protected belief.
If Stella held a firm belief that anything with her name on belonged to her, you would want to be able to sack her from her role in your warehouse for helping herself to crates of beer.
Well taking your examples:
Norman is free to hold whatever opinions he wishes in the privacy of his own head or home. However where those opinions prevent him from doing his job or where they break discrimination laws then his employer is entitled to fire him and the customer entitled to take action for discrimination.
The same goes for Dave.
Stella again can have whatever opinions she wishes in her own head but is breaking the law by theft of beer and her employer is entitled to both fire her and prosecute her.
Expressing an opinion provided it doesn't break the law or incite violence is permissible even if it causes offence to another person. Or makes them uncomfortable.