Stewards for large events are generally provided, in USA, anyhow, by local authorities or are private security people provided by the venue. Their "skills" and discriminatory abilities about what to do or not to do seem hampered often enough.
I'd imagine the same is true in UK.
It's no excuse, especially in the case of the "Liaison Officer" who should have used their authority to sort the mess rather than probably feeling the need to support the stewards, possibly due to their own trans-phobic reactions.
I imagine the LTBG org. was as aghast at the events as we are. But, I suppose they might well have been implicated as well, given the traditional "support" for Ts in the alphabet soup.
But training in issues should definitely be a priority for any service that is going to provide 'security' for LTBG events! The actions of the stewards and the copper were reprehensible.
Nichole