We shouldn't be mean to animals. Is that because animals have rights, like people do? Or is it just because people care about animals?
Vegetarian: no meat, always.
Flexitarian: no meat, sometimes.
A recent Aeon article by Alberto Giubilini makes the case for flexitarianism. Suppose our goal is to reduce overall meat consumption. If we become vegetarians, sure, we won't be eating any meat ourselves. But, we will also be implicitly or explicitly encouraging others to become vegetarians as well. That's a tough sell for many people across the world.
Instead, if we just become flexitarian and encourage others to simply join us in eating less meat, then we'll end up convincing more people and thereby reduce meat consumption overall by a greater amount.
It's a counterintuitive, but plausible argument. Check it out at this link: