I suppose aviation will attract its own set of idiots and self professed experts like any other activty who prefer to shoot off their mouths before engaging brain.
You are right here, although perhaps not quite for the reason you intended. If there were any evidence, even one shred, that mandatory wearing of hi viz vests at a small airfield promoted safety, that would be fine. But there isn't.
In itself Kemble's move may be a small inconvenience. But there is a cumulative effect to all these bad news stories which are making GA in the UK less attractive year by year.
Not one airport in the US, as far as I know, has seen fit to impose a restriction like this, including many where traffic is much busier. No evidence that safety is compromised there either.