Having read the story, the reason given - that funds paid for poppies may not finish in the right hands, seems eminently sensible.
Poppy-wearing is an individual choice.
You cannot have every single car decorated with poppies since some officers may not agree with them, and it is unfair to insist that they drive in a vehicle that suggests that they do agree.
Therefore, individuals can choose to wear a poppy, or not, as they see fit.
That is the sort of freedom of choice that wars were fought for, and its ironic that those who died and whom we remember, may well entirely endorse that choice, and not the wish (ironically!) that one group of individuals feel that everyone should have to remember in a set manner - by wearing a poppy.