Vegetarians and vegans are as bad for the environment as those omnivores who eat Brazilian chickens and beef. If we all turned vegan where would the beans etc come from?
Why would farmers allow deer to wander their land and nosh on their crops if they couldn't get some return from the sale of venison?
Why would they keep the biodiverse grazing meadows, fields and grasslands when they'd get more money ploughing them up and growing beans?
In fact, if we all turned veggie/vegan we would need to plough up all the grass fields in order to grow sufficient plant stuff. There'd be no sheep grazing off beet tops and fertilizing as they go, no outdoor reared pigs cleaning the ground, and fertilizing it at the same time. We would need to feed the soil with chemical fertilizers and the land would lose substance and shrink and there'd be more flooding in low lying areas.
Yes, as a nation we need to eat much less meat. But many of us don't eat a lot, and many of us do buy local, free range, organic. British farmers are responding and looking after the land much better than the previous generation after WW2 when food had to be grown at all cost and too much land was put to the plough. We are, by nature, omnivores.
But, breeding animals purely for unneeded fur is wrong on every level.