Meat doesn’t magically appear. It comes from animals who have just died. But the deaths do not necessarily come via a single means, nor does the consumer necessarily have any bearing on the suffering of the animal or future animals.
I am surprised that anyone would mention “supply and demand” at all given Lemmy has a largely (including myself, just not from a Marxist viewpoint) anti-capitalist demographic, which would mean supply and demand shouldn’t be seen as a necessary factor.