Surely the defining line should be if an activity is legal or not, and therefore eating meat, smoking etc is a legitimate lifestyle choice and should be left to the individual.Consuming animals and animal products goes beyond just being an individual lifestyle choice. That choice causes immense harm and suffering to other species, in which case it is legitimate to openly challenge and oppose that choice.
Again, what are the consequences of the choice to smoke? For instance, on those who choose not to smoke but are subject to second hand smoke? Or the effects on the NHS that the rest of us have to pay for? Or on families/friends left behind by those who smoke themselves into a premature and unpleasant death? The thread isn't about smoking obviously, but there is a line that is crossed by certain "lifestyle" choices and the consequences those choices have for others and in the case of eating animal products, other species.
Can I ask what position would you take if someone was pushing for the ban of alcohol(seeing as there is a number of health and behavouer issuses) would that not be an attack on a legitimate activity.