We need animal testing for medicine
Medical research raises genuinely harder questions than diet does, and the standard definition of veganism already treats them differently. It is also not what the conversation was about.
Modern medicine, from vaccines to cancer drugs, was built on animal research, and much of it still cannot be done any other way, so anyone who takes a prescription is already relying on animals being used for human benefit. If vegans accept that trade-off when human health is at stake, their position is not a clean line against using animals at all but a judgement about when the use is worth it. That makes the stance against eating animals look less like an absolute principle and more like one choice among many that everyone already makes.
Animal research presents a real conflict of interests in a way that eating does: there is, at present, no complete substitute for some forms of testing, and the benefit at stake is human life rather than flavour. Many vegans accordingly take medicines tested on animals, which the 'possible and practicable' formulation accommodates directly.
That said, the comparison does not transfer. The question under discussion is whether to eat animals when nutritionally equivalent alternatives are on the same shelf. Someone who finds animal testing troubling has a reason to support non-animal methods (organ-on-chip systems, computational models) not a reason to continue buying bacon.
Introducing a point that is not relevant to the question under discussion, drawing attention away from it rather than answering it.
How it applies here: Moves from diet, which is the subject, to medical research, which is a different question with a different balance of interests and which veganism's standard definition already handles separately.
Replacing someone's actual position with a weaker, distorted version, then refuting that instead. The original argument is left untouched.
How it applies here: Attributes an absolutist position that the 'as far as is possible and practicable' formulation explicitly does not hold.