Hmmm, got to think about this, it's a subject that does require some reflection.
My first reaction though, FWIW in this here debate, is:
a) I think the Royal British legion were wrong to promote this advertisment and give it their aproval, I think it's come to a sorry state when war is used to try and flog turkeys and brussels sprouts.
b) I'd refute any allegations that playing video games simulating warfare could lead to players being accused of similar sentiments.
Why? I think it would be the same argument that's used where critics accuse video games of causing real life violence, which I believe to be untrue. The greater majority of video game players know it's not for real, it's just fantasy and they are controlling cartoon like characters.
The games are a little like sport, they are competitive, just like those other sporting staples - fencing, shooting, boxing, archery and wrestling.
Human beings, particularly the male of the species, enjoy war games, it's just in our nature, the majority of us played war games involving imaginary weapons when we were younger, in my day we played cowboys and indians (or to be more politically correct - ranch employees and native americans).
As for the advert, I can't say with any real authority but I gather from what I've read that the German/Anglo Christmas Day game of football is just a myth, likely dreamed up by some over-sentimental twerp trying to tug at heartstrings. Which is what this ad is so blatantly trying to do (and succeeding, by the sound of it).
I know that if I was taking part in that war and I'd had endless weeks of suffering all the conditions and horror that went with it, I'd positively hate the enemy and rather than have a friendly game of football with him I'd simply want to kill him. That's the way it was - and is, in war.
Anyhow, that's my knee jerk reaction, but youse two have made me step back and think, which is a good thing.
Coda: All ads and correspondence I receive with reference to the celebration taken by the majority of folk on this fair isle every December 25th now gets the same level of ignore from me as any ad proclaiming 'Hurry!' or 'Last chance!'. Until December 1st anyway.
And that includes Sainsburys