It's good to work out in your own head or discuss why 'be kind' is irrelevant.
But honestly, if someone uses that line then generally whether they mean it to be or not, it's just a diversion, don't go there, there's no point arguing it. It's meaningless.
'Women's prisons should be single sex for their safety'
'be kind' - in what way does this address the issue? It's meaningless.
'Women should be entitled to ask for and get a female HCP'
'be kind' - this is not relevant.
'Children should be given factual information about sex and not be told their clothes/toys have any bearing on their being a girl or a boy'
'be kind' - again, it's just meaningless.
I suppose it's a kind of tone policing. A way to stop the issues from being discussed.
It's also not 'kindness' to suggest that 'transitioning' will solve childrens' problems - as far as I'm aware the Tavistock's own research suggested mental health outcomes were worse after transitioning.
'Kindness' isn't always about pandering, or pretending, or going along with something. Kindness (which I value greatly) sometimes involves upsetting boats, telling the truth even though it's difficult, asking questions instead of turning a blind eye. Real, genuine kindness means connecting with honesty and compassion, not just doing what you're told in case someone gets upset. That isn't kindness, it's emotional manipulation/blackmail, and no good for anyone.