Oh i don't think you are BU OP.
Lots of things on sale around a supermarket could be potentially dangerous. A child would have to be unsupervised for a few moments for it to open and drink a harmful substance for eg. though.
But a big sharp knife has the capacity to be very dangerous the moment a child closes their fingers over it. Or, as you say, OP, to be used or stolen as an instant weapon in the heat of the moment.
I'm surprised so many posters are prepared to say that the principal of 'parent should be watching' trumps the risk to a small child from sharp knives within their reach. The child, after all, is not at fault if they have a parent who's not paying attention.