But that's true of any post about animal ownership, if you think about it. Somebody puts a post up about a cute cat they've got from a rescue and somebody else thinks, 'ooh, I'd like a cat', but buys one from Gumtree, or gets a dog from a puppy farm.
So should we never post about our pets because someone, somewhere might be inspired to get one without giving thought to the negative industry they perpetuate? Or, as may be the case, how they will look after said animal for the years to come.
My own rescue cat was likely dumped by seasonal workers. It's not uncommon in the tourist area we were living in at the time. Perhaps those people saw pictures of cute cats posted up by responsible owners and thought they'd like one without considering what happens when they move on.
People are motivated to have pets for all sorts of reasons. Believe it or not, some people see posts about how dangerous XL bullies are and find that is a motivation to get one.
So perhaps we simply shouldn't share our animal stories at all, because there are thoughtless and irresponsible people who might just see them and be inspired in the wrong way.
I don't disagree with your points about the importance of neutering/spaying. I just think pissing on this particular bonfire because some irresponsible people might be negatively inspired is somewhat disingenuous.