That's a completely flawed analogy. This is like seeing a smoker who smokes a pack a day and saying "could you try half a pack and be that much safer?"

In this analogy, you come along and say "don't bother, you're gonna get lung cancer and die anyway."

I think that's fair, but to a heavy smoker living on a pack a day, I indeed would recommend total abstinence for ideal health - not merely reducing to half-harm. Though it may seem like the softer reduction approach would be more supported, I believe it only serves as a mechanism for the smoker to lose control and relapse again and again. It is a subjective philosophy, so I don't expect we'll totally agree, but I thank you for the discussion.

Counterexample: I'm lacto-ovo vegetarian but not vegan partly because the anxiety and stress involved in checking ingredients for ethical purity, or worrying about honey or bone-bleached sugar or rennet in cheese, is not good for me.

I see what you're saying -- that's true in the case of addiction. I don't know that addiction is the right model for consumption of animal products, given that you can reduce your consumption of them (I have!) without triggering as much of a biological feedback loop geared to get you to increase consumption. It's not a totally inappropriate metaphor, though. I agree, we probably just have a difference of approach here.

I'd still suggest that delivering the message in a way that is more empathetic towards the person trying to make the change would be likely to get better results in terms of changing minds.

Except we have smoking AND meat substitutes but don't let reality stop you from having fun