At the very least, the explanation given by the British Legion is more in line with intelligent application of the trademark they are granted: "infringing its trademark by commercially benefiting from...".
In the "RCL Whither..." thread, someone posted about the Canadian Legion bitchin' and throwing its "trademark weight" at a poor bakery which, at specific request of one individual purchaser made for his/her own private purpose, baked a single cake in the shape of a remembrance day poppy. That is not "commercially benefiting from the use of the poppy. If that bakery, without anyone's specific request had baked half a dozen of them and put them on display for sale in the days leading to November 11, that would be different.
The analogy here is the same difference as someone going to a baker and ordering a Donald Duck cake for his kid's birthday instead of baking it himself, for which Disney would have no recourse, or the same bakery baking half a dozen Donald Duck cakes once a week for general display and sale, which would be infringement.