While I agree that the military is a career choice and deserves no more recognition than any other public service you are categorically wrong in the way you imply that the military doesn't routinely protect the citizens of the UK, either from direct or indirect attack, just because something is not reported or in the public eye doesn't mean that your safety and freedoms are not being protected. I also think you are living in the clouds if you think that a federal Europe will come about in the next two decades or anything resembling a unified European Armed Forces.
As far as the arrest of the kid goes, I didn't join the forces so that kids like that could be arrested for expressing themselves in such a way. Burning a poppy may be disrespectful in the context of the Armistice, but the whole point of remembrance is that these people died to protect that kids right to express himself, so I don't know which I find more offensive, the poppy burning or the arrest itself.