So the entire country will not be eating only meat-based sides?
I have really lost the convoluted plot of what your argument is now. I am not sure you even know. You are just being like a dog with a bone for the hell of it.
No-one is serving ONLY 'meat-based sides.' With the possible exception of a sausagemeat stuffing or pigs in blankets, most sides are not meat based. My carrots and parsnips and sauces and cabbage or other veg (if I make them) don't contain meat product. My sprouts don't always contain bacon but they sometimes do. My stuffing rarely contains sausagemeat as I find it a bit too rich when there are pigs in blankets as well. Although my stuffing and gravy always contain at least some chicken/turkey stock because it's a deeper more interesting flavour than using water.
That doesn't make them 'meat based side dishes', it just makes it a non-vegetarian side dishes. But it's easy enough to not use any meat fat/juices if you prefer. I honestly don't care which people choose to do, I just know what my family prefers, I know what most chefs would do.
No-one has tried to say that 'the entire country' does any one thing. The entire country can't even agree on whether they want turkey or not. Even if you take away the people who do not eat a traditional British Christmas dinner at all, and just focus on those who do, there is still no such thing as 'an entire country' of people eating the exact same thing. There are many variations and nuances on a theme peas and sweetcorn. yorkshire pudding with turkey cauliflower cheese. mashed potato All an anathema to me with my Christmas turkey, but each to their own.
But that doesn't change the fact that most people will be cooking the same bloody things as me because they are traditional, and many many of them will be using meat juices and animal fats to baste their roasted veg, or to enhance their gravies, and possibly putting some bacon in their sprouts. Telling people that the most important meal of their year is a 'weird tradition' using 'bizarre' methods that result in that result in 'bland' food is just rude and goady.
On the other hand, I imagine the number of people serving semi-raw broccoli in soy sauce as a side on to a Christmas roast can be counted on one hand. Or one finger. But if you like it, knock yourself out.