In other words, anti-trans (or GC) beliefs occupy much the same position in law as anti-gay Christian beliefs. You can /believe/ them all you like & can’t be sacked for that belief, but if you express those beliefs in the workplace you’ve just created a hostile environment for other employees & your employer can simply fire you (after going through the appropriate disciplinary procedures where required by law) due to your breach of the Equality Act, under which being trans (specifically in law: gender reassignment) carries protected status in the same way that being a different skin colour or sexuality does.