It is reasonable to expect the Police to answer questions about their officer's use of police time
I don't know if that officer is still serving (The article uses the past tense and Google doesn't help) However even if they're still a warranted officer there is nothing whatsoever to suggest they are using "police time" to campaign.
When a police officer sets up a political pressure group that, as evidenced in the Transgendertrend post, chooses to out a school publicly in an attempt to force it to change it's policies in favour of one child, then it is reasonable to question whether the police are making policy
No it's not. If an official police account, or if a person stating they're acting on behalf of the police did this you'd have a point. This is a transgender charity, nothing to do with the police, other than it's founder being a serving/retired officer. If the founder of the charity was a security guard would you claim the security industry authority were making policy? Of course not. You are being disingenuous and you know it!
The Police are not and should not be, agents of social change.
Agreed. However this board did not seem to have an issue when the Notts police CC decided to record misogyny as a hate crime, when she had absolutely no legal power to act on it. Do you believe the Notts CC was right to record misogyny as a hate crime?