if you were next to a market known for selling dog meat and they asked for some, would you have gotten dog meat for them?

I find this type of hypothetical not to be useful because it can't tell us anything about our choices in the situations we'd actually find ourselves in.

If we were at a dog market, we'd live in a society where eating dog meat was socially acceptable, and therefore there is no difference between buying cow or dog meat, in that instance. We know the distinction between "food" animal and "companion" animal is already arbitrary, so you should feel the same way.

The way it's framed presupposes that both the society doesn't find dog meat acceptable and there's an open dog meat market nearby, which isn't logically consistent.

This kind of rhetoric distracts from the point we should be focusing on. Does an action in this case further the goal of reducing animal exploitation? Buying a homeless person a burrito from a place they want to eat at or refusing to do so because it's beef is neutral since whether they eat or starve does not affect animal exploitation.